Datenblatt für STS1TXQTR von STMicroelectronics

Datenblatt - Kommentare/Fehler melden

This is information on a product in full production.

August 2013 DocID025109 Rev 1 1/70

STS1TX

Low data-rate, low power sub-1GHz transmitter

Datasheet - production data

Features

•Frequency bands: 150-174 MHz, 300-348

MHz, 387-470 MHz, 779-956 MHz

•Modulation schemes: 2-FSK, GFSK, MSK,

GMSK, OOK, and ASK

•Air data rate from 1 to 500 kbps

•Very low power consumption (21 mA TX at +11

dBm)

•Programmable channel spacing (12.5 kHz

min.)

•Programmable output power up to +16 dBm

•Fast startup and frequency synthesizer settling

time (6 µs)

•Integrated temperature sensor

•Battery indicator and low battery detector

•TX FIFO buffer (96 bytes each)

•Configurability via SPI interface

•AES 128-bit encryption co-processor

•Fully integrated ultra low power RC oscillator

•Wakeup on internal timer and on external event

•Flexible packet length with dynamic payload

length

•Automatic CRC handling

•FEC with interleaving

•Whitening of data

•Wireless M-BUS, EN 300 220, FCC CFR47 15

(15.205, 15.209, 15.231, 15.247, 15.249), and

ARIB STD T-67, T93, T-108 compliant

•QFN20 4x4 mm RoHS package

•Operating temperature range from -40 °C to

85 °C

Applications

•AMR (automatic meter reading)

•Home and building automation

•WSN (wireless sensors network)

•Industrial monitoring and control

•Wireless fire and security alarm systems

•Point-to-point wireless link

QFN20

Table 1. Device summary

Order code Package Packing

STS1TXQTR QFN20 Tape and reel

www.st.com

Contents STS1TX

2/70 DocID025109 Rev 1

Contents

1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3 Typical application diagram and pin description . . . . . . . . . . . . . . . . . . 7

3.1 Typical application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4 Pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5 Absolute maximum ratings and thermal data . . . . . . . . . . . . . . . . . . . 11

6 Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6.1 General characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6.2 Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6.2.1 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6.2.2 Digital SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

6.2.3 RF transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

6.2.4 Crystal oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

6.2.5 Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

7 Operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

7.1 Reset sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

7.2 Timer usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

8 Block description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

8.1 Power management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

8.1.1 Switching frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

8.2 Power-on-reset (POR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

8.3 Low battery indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

8.4 Voltage reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

8.5 Oscillator and RF synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

8.6 RCO: features and calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

8.6.1 RC oscillator calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

8.7 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

DocID025109 Rev 1 3/70

STS1TX Contents

8.8 Temperature sensors (TS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

8.9 AES encryption co-processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

9 Transmission and reception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

9.1 PA configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

9.2 RF channel frequency settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

9.3 Modulation scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

9.3.1 Data rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

9.4 Data coding and integrity check process . . . . . . . . . . . . . . . . . . . . . . . . . 39

9.4.1 FEC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

9.4.2 CRC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

9.4.3 Data whitening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

9.4.4 Data padding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

9.5 Packet handler engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

9.5.1 STack packet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

9.5.2 Wireless M-Bus packet (W M-BUS, EN13757-4) . . . . . . . . . . . . . . . . . . 43

9.5.3 Basic packet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

9.6 Data modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

9.7 Data FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

9.8 Frequency hopping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

10 MCU interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

10.1 Serial peripheral interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

10.2 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

10.3 GPIOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

10.4 MCU clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

11 Register table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

12 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

13 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

List of tables STS1TX

4/70 DocID025109 Rev 1

List of tables

Table 1. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Table 2. Description of the external components of the typical application diagram . . . . . . . . . . . . . 9

Table 3. BOM for different bands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Table 4. Pinout description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Table 5. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Table 6. Thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Table 7. Recommended operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Table 8. General characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Table 9. Power consumption static modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Table 10. Power consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Table 11. Digital SPI input and output (SDO, SDI, SCLK, CSn, and SDN) and

GPIO specification (GPIO_1-4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Table 12. RF transmitter characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Table 13. Crystal oscillator characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Table 14. Ultra low power RC oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Table 15. N-Fractional Σ∆ frequency synthesizer characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Table 16. Analog temperature sensor characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Table 17. Battery indicator and low battery detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Table 18. States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 19. Commands list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Table 20. POR parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Table 21. STS1TX timers description and duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Table 22. SMPS configuration settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Table 23. Programmability of trans-conductance at startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Table 24. CP word look-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table 25. RC calibrated speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Table 26. PA_level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Table 27. Frequency threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Table 28. SPI interface timing requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Table 29. Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Table 30. Digital outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Table 31. Digital inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Table 32. MCU_CK_CONF configuration register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Table 33. MCU clock vs. state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Table 34. General configuration registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Table 35. Radio configuration registers (analog blocks). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Table 36. Radio configuration registers (digital blocks) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Table 37. Packet/protocol configuration registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Table 38. Frequently used registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Table 39. General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

Table 40. QFN20 (4 x 4 mm.) mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Table 41. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

DocID025109 Rev 1 5/70

STS1TX List of figures

List of figures

Figure 1. STS1TX block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 2. Suggested application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 3. Application diagram for TX boost mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 4. Diagram and transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 5. Power-on reset timing and limits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Figure 6. Shaping of ASK signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Figure 7. Output power ramping configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 8. LFSR block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Figure 9. Threshold of the linear FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Figure 10. SPI “write” operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Figure 11. SPI “read” operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Figure 12. SPI “command” operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Figure 13. QFN20 (4 x 4 mm.) drawing dimension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Description STS1TX

6/70 DocID025109 Rev 1

1 Description

The STS1TX is a very low-power RF transmitter intended for RF wireless applications in the

sub-1 GHz band. It is designed to operate both in the license-free ISM and SRD frequency

bands at 169, 315, 433, 868, and 915 MHz, but can also be programmed to operate at other

frequencies in the 300-348, 387-470, and 779-956 MHz bands. The air data rate is

programmable from 1 to 500 kbps, and the STS1TX can be used in systems with channel

spacing of 12.5/25 kHz, complying with the EN 300 220 standard. It uses very few discrete

external components and integrates a configurable baseband modem, which supports data

management and modulation. The data management handles the data in the proprietary

fully-programmable packet format, and also allows the M-Bus standard compliance format

(all performance classes).

An AES 128-bit encryption co-processor is available for secure data transfer. The STS1TX

supports different modulation schemes: 2-FSK, GFSK, OOK, ASK, and MSK. Transmitted

data bytes are buffered in FIFO (TX FIFO), accessible via the SPI interface for host

processing.

DocID025109 Rev 1 7/70

STS1TX Introduction

2 Introduction

A simplified block diagram of the STS1TX is shown in Figure 1.

Figure 1. STS1TX block diagram

The transmitter part of the STS1TX is based on direct synthesis of the RF frequency. The

power amplifier (PA) input is the LO generated by the RF synthesizer, while the output level

can be configured between -30 dBm and +11 dBm in 0.5 dB steps. The data to be

transmitted can be provided by an external MCU either through the 96-byte TX FIFO

writable via SPI, or directly using a programmable GPIO pin. The STS1TX supports

frequency hopping, extending the link range and improving performance.

The STS1TX has a very efficient power management (PM) system.

An integrated switched mode power supply (SMPS) regulator allows operation from a

battery voltage ranging from +1.8 V to +3.6 V, and with power conversion efficiency of at

least 80%.

A crystal must be connected between XIN and XOUT. It is digitally configurable to operate

with different crystals. As an alternative, an external clock signal can be used to feed XIN for

proper operation. The STS1TX also has an integrated low-power RC oscillator, generating

the 34.7 kHz signal used as a clock for the slowest timeouts (i.e. sleeping and backoff).

A standard 4-pin SPI bus is used to communicate with the external MCU. Four configurable

general purpose I/Os are available.

PA FREQ

SYNTH

MODULATOR

TX FIFOs

SPI

REGISTERS MAP

GPIO

INTERFACE

ATB

RADIO CONTROL

RCO

ΔΣ

DATA LINK LAYER

Digital LDO

VCO LDO

PLL LDO

PROG LDO

ADC LDO

Low Power

Digital LDO

TEMP SENS

SDO

SDI

SCLK

CSn

GPIO_3

GPIO_2

GPIO_1

GPIO_0

VR DIG

VDD DIG

XIN

XOUT

SDN

GND PA

POR

AES

LDO

1V5

CENTRAL

BIAS

BOR

(raw)

BOR

(acc)

BLD

DIGITAL CLOCK

OUTDiv LDO

SMPS

DIG

I/O

1/2

LoopDiv LDO

GAMS080520131020FSR

413—4“ 02 4 MN C11 3—’“‘——| |—-—II‘ u; cu “—4“ in a 7 PH“ |—-—h L3 4 Hail-w ca 4' cwsnamm 3M20F§R

Typical application diagram and pin description STS1TX

8/70 DocID025109 Rev 1

3 Typical application diagram and pin description

3.1 Typical application diagram

This section describes different application diagrams for the STS1TX that can be used

based on customer requirements. In particular, Figure 2 shows the default configuration and

Figure 3 shows the TX boost mode configuration. The default configuration provides the

best power consumption figures. The TX boost mode configuration is used to increase TX

output power.

Figure 2. Suggested application diagram

1 GPIO_0 SDN 15

SMPS Ext1 14

SMPS Ext2 13

TX 12

GND PA 11

2 SDO

3 SDI

4 SCLK

5 CSn

GPIO_1 20

GPIO_2 19

GPIO_3 18

VR DIG 17

VDD SMPS 16

8 VDD DIG

6 XOUT

7 XIN

9 N.C.

10 N.C.

DIGITAL INTERFACE

1.8V - 3.6V power supply

Spirit1 TX

DIE ATTACH PAD:

Antenna

(50Ω)

STS1TX

GAMS080520131120FSR

E] L9 % I—Hr‘ —| I—Hr‘ c1) W4 |—-—lr‘ L0 :15 -—| I—o—dr‘ é“ a :I—o—lw E? H“ GIL—flaw 4? chsaueazmuzaFSR

DocID025109 Rev 1 9/70

STS1TX Typical application diagram and pin description

Figure 3. Application diagram for TX boost mode

Table 2 covers all the frequency bands using a set of different external components as

shown in Table 3: BOM for different bands.

Table 2. Description of the external components of the typical application diagram

Components Description

C0 Decoupling capacitor for on-chip voltage regulator to digital part

C1, C2, C3, C14, C15 RF LC filter/matching capacitors

C8 Matching DC blocking capacitors

C9, C10 Crystal loading capacitors

C11, C12, C13 SMPS LC filter capacitor

L0 RF choke inductor

L1, L2, L3, L9 RF LC filter/matching inductors

XTAL 24, 26, 48, 52 MHz

1 GPIO_0 SDN 15

SMPS Ext1 14

SMPS Ext2 13

TX 12

GND PA 11

2 SDO

3 SDI

4 SCLK

5 CSn

GPIO_1 20

GPIO_2 19

GPIO_3 18

VR DIG 17

VDD SMPS 16

8 VDD DIG

6 XOUT

7 XIN

9 N.C.

10 N.C.

DIGITAL INTERFACE

1.8V - 3.6V power supply

Spirit1 TX

DIE ATTACH PAD:

Antenna

(50Ω)

1.8V - 3.6V power supply

STS1TX

GAMS080520131124FSR

Typical application diagram and pin description STS1TX

10/70 DocID025109 Rev 1

Table 3. BOM for different bands

Ref

design

(1)

170 MHz band 315 MHz band 433 MHz band 868 MHz band 915/922 MHz band

STEVAL-

IKRV001V1

STEVAL-

IKRV001V2

STEVAL-

IKRV001V3

STEVAL-

IKRV001V4 STEVAL-IKRV001V5

Comp. Supplier Value Supplier Value Supplier Value Supplier Value Supplier Value

C0 Murata 100nF Murata 100nF Murata 100nF Murata 100nF Murata 100nF

C1 Murata 18pF Murata 12pF Murata 8.2pF NE Murata 7pF

C2 Murata 27pF Murata 27pF Murata 18pF Murata 8.2pF Murata 2.4pF

C3 Murata 4.3pF Murata 15pF Murata 10pF Murata 5.6pF Murata 3.6pF

C8 Murata 390pF Murata 220pF Murata 220pF Murata 220pF Murata 220pF

C9 Murata 12pF Murata 12pF Murata 12pF Murata 12pF Murata 12pF

C10 Murata 10pF Murata 10pF Murata 10pF Murata 10pF Murata 10pF

C11 Murata 1µF Murata 1µF Murata 1µF Murata 470nF Murata 1µF

C12 Murata 100nF Murata 100nF Murata 100nF Murata 100nF Murata 100nF

C13 Murata 560pF Murata 330pF Murata 330pF Murata 330pF Murata 330pF

C14 Murata 220pF Murata 1.8pF Murata 1.8pF Murata 1.2pF NE

C15 Murata 6.2pF Murata 1.2pF NE NE NE

L0 Murata 200nH Murata 220nH Murata 150nH Murata 100nH Murata 100nH

L1 Coilcraft 39nH Murata 12nH Murata 8.2nH Murata 3nH Murata 3.6nH

L2 Coilcraft 56nH Murata 12nH Murata 10nH 0R0

(resistor) Murata 5.1nH

L3 Murata 3.6pF

(cap.) Murata 15nH Murata 10nH Murata 4.3nH Tyco

Electronics 0R0

L9 Coilcraft 51nH Murata 15nH Murata 6.2nH Murata 2.7nH NE

XTAL NDK 25 MHz NDK 50

MHz NDK 50 or 52

MHz NDK

50 or

MHz

1. For complete BOM including part numbers, please check the corresponding reference design.

DocID025109 Rev 1 11/70

STS1TX Pinout

4 Pinout

Table 4. Pinout description

Pin Name I/O Description

1 GPIO_0 I/O See description of GPIOs below

2 MISO O SPI data output pin

3 MOSI I SPI data input pin

4 SCLK I SPI clock input pin

5 CSn I SPI chip select

6XOUTO

Crystal oscillator output. Connect to an external 26 MHz crystal or

leave floating if driving the XIN pin with an external signal source

7XINI

Crystal oscillator input. Connect to an external 26 MHz crystal or to

an external source. If using an external clock source with no crystal,

DC coupling with a nominal 0.2 VDC level is recommended with

minimum AC amplitude of 400 mVpp.

The instantaneous level at input cannot exceed the 0 - 1.4 V range.

8 VBAT VDD +1.8 V to +3.6 V input supply voltage

9NC-

10 NC -

11 GND_PA GND Ground for PA.

To be carefully decoupled from other grounds.

12 TX O RF output signal

13 SMPS Ext2 I Regulated DC-DC voltage input

14 SMPS Ext1 O DC-DC output pin

15 SDN I

Shutdown input pin. 0-VDD V digital input. SDN should be = ‘0’ in all

modes except shutdown mode. When SDN =’1’ the STS1TX is

completely shut down and the contents of the registers are lost.

16 VBAT VDD +1.8 V to +3.6 V input supply voltage

17 VREG(1) VDD Regulated output voltage. A 100 nF decoupling capacitor is required

18 GPIO3 I/O General purpose I/O that may be configured through the SPI

registers to perform various functions, including:

– MCU clock output

– FIFO status flags

– Wakeup input

– Battery level detector

– Temperature sensor output

19 GPIO2 I/O

20 GPIO1 I/O

21 GND GND Exposed pad ground pin

1. This pin is intended for use with the STS1TX only. It cannot be used to provide supply voltage to other

devices.

Absolute maximum ratings and thermal data STS1TX

12/70 DocID025109 Rev 1

5 Absolute maximum ratings and thermal data

Absolute maximum ratings are those values above which damage to the device may occur.

Functional operation under these conditions is not implied. All voltages are referred to GND.

Table 5. Absolute maximum ratings

Pin Parameter Value Unit

8,14,16 Supply voltage and SMPS output -0.3 to +3.9 V

17 DC voltage on VREG -0.3 to +1.4 V

1,3,4,5,15,18,19,20 DC voltage on digital input pins -0.3 to +3.9 V

2 DC voltage on digital output pins -0.3 to +3.9 V

11 DC voltage on analog pins -0.3 to +3.9 V

6,7 DC voltage on XTAL pins -0.3 to +1.4 V

13 DC voltage on SMPS Ext2 pin -0.3 to +1.8 V

12 DC voltage on TX pin -0.3 to +3.9 V

TSTG Storage temperature range -40 to +125 °C

VESD-HBM Electrostatic discharge voltage ±1.0 KV

Table 6. Thermal data

Symbol Parameter QFN20 Unit

Rthj-amb Thermal resistance junction-ambient 45 °C/W

Table 7. Recommended operating conditions

Symbol Parameter Min. Typ. Max. Unit

VBAT Operating battery supply voltage 1.8 3 3.6 V

TAOperating ambient temperature range -40 85 °C

DocID025109 Rev 1 13/70

STS1TX Characteristics

6 Characteristics

6.1 General characteristics

6.2 Electrical specifications

6.2.1 Electrical characteristics

Characteristics measured over recommended operating conditions unless otherwise

specified. Typical values are referred to TA = 25 °C, VBAT = 3.0 V. All performance is referred

to a 50 Ohm antenna connector, via the reference design using the application diagram as

in Figure 2, unless otherwise noted.

Table 8. General characteristics

Symbol Parameter Min. Typ. Max. Unit

FREQ Frequency range

150

174 MHz

300 348 MHz

387 470 MHz

779 956 MHz

Air data rate for each modulation scheme.

Note that if “Manchester”, “3-out-of-6” and/or FEC encoding/decoding options are

selected, the effective bit rate will be lower.

2-FSK 1

500 kBaud

GMSK (BT=1, BT=0.5) 1 500 kBaud

GFSK (BT=1, BT=0.5) 1 500 kBaud

MSK 1 500 kBaud

OOK/ASK 1 250 kBaud

Table 9. Power consumption static modes

Symbol Parameter Test conditions Min. Typ. Max. Unit

IBAT Supply current

Shutdown (1)

1. See Table 18.

2.5

nAStandby (1) 600

Sleep (1) 850

Ready (default mode)(1) 400 µA

Lock(1) 4.4 mA

Characteristics STS1TX

14/70 DocID025109 Rev 1

6.2.2 Digital SPI

Table 10. Power consumption

Symbol Parameter Test conditions SMPS ON SMPS OFF Unit

IBAT Supply current

TX (1)(2) +16 dBm 169 MHz

1. See table Table 18.

2. TX boost mode configuration VBAT = 3.6 V.

TX (1)(2) +16 dBm 315 MHz 52

TX (1)(2) +16 dBm 433 MHz 49.3

TX (1)(2) +15.5 dBm 868 MHz 44

TX (1)(2) +16 dBm 920 MHz 45.2

TX (1) +11 dBm 169 MHz 18 33

TX (1) +11 dBm 315 MHz 22 37

TX (1) +11 dBm 433 MHz 19.5 33

TX (1) +11 dBm 868 MHz 21 41

TX (1) +11 dBm 920 MHz 20 39

TX (1) -8 dBm 169 MHz 6

TX (1) -8 dBm 315 MHz 6.5

TX (1) -7 dBm 433 MHz 7

TX (1) -7 dBm 868 MHz 7

Table 11. Digital SPI input and output (SDO, SDI, SCLK, CSn, and SDN) and GPIO

specification (GPIO_1-4)

Symbol Parameter Test condition Min. Typ. Max. Unit

fclk Clock frequency 10 MHz

CIN Port I/O capacitance 1.4 pF

TRISE Rise time

0.1*VDD to 0.9*VDD,

CL=20 pF (low output

current programming)

6.0

0.1*VDD to 0.9*VDD,

CL=20 pF (high output

current programming)

2.5

TFALL Fall time

0.1*VDD to 0.9*VDD,

CL=20 pF (low output

current programming)

7.0

0.1*VDD to 0.9*VDD,

CL=20 pF (high output

current programming)

2.5

VIH

Logic high level input

voltage

VDD/2

+0.3 V

DocID025109 Rev 1 15/70

STS1TX Characteristics

6.2.3 RF transmitter

Characteristics measured over recommended operating conditions unless otherwise

specified. All typical values are referred to TA = 25 °C, VBAT = 3.0 V. All performance is

referred to a 50 Ohm antenna connector, via the reference design.

VIL

Logic low level input

voltage

VDD/8

+0.3 V

VOH High level output voltage

IOH = -2.4 mA (-4.2 mA if

high output current

capability is

programmed).

(5/8)*

VDD+

0.1

VOL Low level output voltage

IOL = +2.4 mA (+4 mA if

high output current

capability is

programmed).

0.5 V

Table 11. Digital SPI input and output (SDO, SDI, SCLK, CSn, and SDN) and GPIO

specification (GPIO_1-4) (continued)

Symbol Parameter Test condition Min. Typ. Max. Unit

Table 12. RF transmitter characteristics

Symbol Parameter Test conditions Min. Typ. Max. Unit

PMAX_TX_BO

OST

Maximum output

power(1)

Delivered to a 50 Ohm single-ended

load via reference design using TX

boost mode configuration

-16 dBm

PMAX

Maximum output

power(1)

Delivered to a 50 Ohm single-ended

load via reference design -11 dBm

PMIN Minimum output power Delivered to a 50 Ohm single-ended

load via reference design - -30 dBm

PSTEP Output power step - 0.5 dB

Characteristics STS1TX

16/70 DocID025109 Rev 1

PSPUR,ETSI

Unwanted emissions

according to ETSI

EN300 220-1(harmonic

included, using

reference design)

RF = 170 MHz, frequencies below 1

GHz - -36 dBm

RF = 170 MHz, Frequencies above 1

GHz -< -60 dBm

RF = 170 MHz, frequencies within

47-74, 87.5-108,174-230,470-862

MHz

- -55 dBm

RF = 434 MHz, frequencies below 1

GHz - -42 dBm

RF = 434 MHz, Frequencies above 1

GHz - -46 dBm

RF = 434 MHz, frequencies within

47-74, 87.5-108,174-230,470-862

MHz

- -61 dBm

RF = 868 MHz, frequencies below 1

GHz - -51 dBm

RF = 868 MHz, Frequencies above 1

GHz - -40 dBm

RF = 868 MHz, frequencies within

47-74, 87.5-108,174-230,470-862

MHz

- -54 dBm

Table 12. RF transmitter characteristics (continued)

Symbol Parameter Test conditions Min. Typ. Max. Unit

DocID025109 Rev 1 17/70

STS1TX Characteristics

PSPUR,FCC

Unwanted emissions

according to FCC part

15(harmonic included,

using reference design)

RF = 310-320 MHz, harmonics

(measured with max output power) - -37 dBm

RF = 310-320 MHz, 1.705 MHz <f<

30 MHz -<-60 dBm

RF = 310-320 MHz, 30 MHz <f< 88

MHz -<-60 dBm

RF = 310-320 MHz, 88 MHz <f< 216

MHz -<-60 dBm

RF = 310-320 MHz, 216 MHz <f<

960 MHz -<-60 dBm

RF = 310-320 MHz, 960 MHz <f - <-60 dBm

RF = 902-928 MHz, 1.705 MHz <f<

30 MHz (@ max output power) -<-70 dBm

RF = 902-928 MHz, 30 MHz <f< 88

MHz (@ max output power) -<-70 dBm

RF = 902-928 MHz, 88 MHz <f< 216

MHz (@ max output power) -<-70 dBm

RF = 902-928 MHz, 216 MHz <f<

960 MHz (@ max output power) - -52 dBm

RF = 902-928 MHz, 960 MHz <f (@

max output power) - -41 dBm

2nd and 7th harmonics - -25 dBc

Table 12. RF transmitter characteristics (continued)

Symbol Parameter Test conditions Min. Typ. Max. Unit

Characteristics STS1TX

18/70 DocID025109 Rev 1

PSPUR,ARIB

Unwanted emissions

according to ARIB

RF = 312-315 MHz, frequency below

1 GHz (@ max output power,

according to ARIB STD-T93)

- -41 dBm

RF = 312-315 MHz, frequency above

1 GHz (@ max output power,

according to ARIB STD-T93)

- -48 dBm

RF = 426-470 MHz (@ max output

power, according to ARIB STD-T67) -<-40dBm

RF = 915-917 MHz and

RF = 920-930 MHz, f< 710 MHz (@

max output power, according to ARIB

STD-T108)

-<-55dBm

RF = 915-917 MHz and

RF = 920-930 MHz, 710 MHz <f<

915 MHz (@ max output power,

according to ARIB STD-T108)

- -55 dBm

RF = 915-917 MHz and

RF = 924-930 MHz, 915 MHz <f<

930 MHz (@ max output power,

according to ARIB STD-T108)

- -36 dBm

RF = 920-924 MHz, 915 MHz <f<

920.3 MHz (@ max output power,

according to ARIB STD-T108)

-<-36dBm

RF = 920-924 MHz, 920.3 MHz <f<

924.3 MHz (@ max output power,

according to ARIB STD-T108)

- -55 dBm

RF = 920-924 MHz, 924.3 MHz <f<

930 MHz (@ max output power,

according to ARIB STD-T108)

- -36 dBm

RF = 915-917 MHz and

RF = 920-930 MHz, 930 MHz <f<

1000 MHz (@ max output power,

according to ARIB STD-T108)

- -55 dBm

RF = 915-917 MHz and

RF = 920-930 MHz, 1000 MHz <f<

1215 MHz (@ max output power,

according to ARIB STD-T108)

-<-60dBm

RF = 915-917 MHz and

RF = 920-930 MHz, 1215 MHz <f (@

max output power, according to ARIB

STD-T108)

- -38 dBm

Table 12. RF transmitter characteristics (continued)

Symbol Parameter Test conditions Min. Typ. Max. Unit

DocID025109 Rev 1 19/70

STS1TX Characteristics

6.2.4 Crystal oscillator

Characteristics measured over recommended operating conditions unless otherwise

specified. All typical values are referred to TA = 25 °C, VBAT = 3.0 V. Frequency synthesizer

characteristics are referred to 915 MHz band.

PHARM Harmonics level

RF = 170 MHz, 2nd harmonic (max

power level) --36

dBm

RF = 170 MHz, 3rd harmonic (max

power level) --55

RF = 315 MHz, 2nd harmonic (max

power level) --52

dBc

RF = 315 MHz, 3rd harmonic (max

power level) --52

RF = 433 MHz, 2nd harmonic (max

power level) --43

dBm

RF = 433 MHz, 3rd harmonic (max

power level) --46

RF = 868 MHz, 2nd harmonic (max

power level) --40

RF = 868 MHz, 3rd harmonic (max

power level) --42

RF = 915 MHz, 2nd harmonic (max

power level) - -28 dBc

RF = 915 MHz, 3rd harmonic (max

power level) --42

dBm

RF = 922 MHz, 2nd harmonic (max

power level) --39

RF = 922 MHz, 3rd harmonic (max

power level) --60

PALOAD

Optimum load

impedance (simulated

v a l u e s )

170 MHz, using reference design - 46 +

j36 Ohm

315 MHz, using reference design - 25 +

j27 Ohm

433 MHz, using reference design - 29 +

j19 Ohm

868 MHz, using reference design - 34 - j7 Ohm

915 MHz, using reference design - 15 +

j28 Ohm

922 MHz, using reference design - 42 -

j15 Ohm

1. In ASK/OOK modulation, indicated value represents peak power.

Table 12. RF transmitter characteristics (continued)

Symbol Parameter Test conditions Min. Typ. Max. Unit

Characteristics STS1TX

20/70 DocID025109 Rev 1

Table 13. Crystal oscillator characteristics

Symbol Parameter Test conditions Min. Typ. Max. Unit

XTALFCrystal frequency Range 1

Range 2

52 MHz

FTOL Frequency tolerance(1)

1. Including initial tolerance, crystal loading, aging, and temperature dependence. The acceptable

crystal tolerance depends on RF frequency and channel spacing/bandwidth.

± 40 ppm

PNXTAL

Minimum requirement on

external reference phase

noise mask (Fxo=26 MHz),

to avoid degradation on

synthesizer phase/noise

100 Hz -90 dBc/Hz

1 kHz -120 dBc/Hz

10 kHz -135 dBc/Hz

100 kHz -140 dBc/Hz

1 MHz -140 dBc/Hz

TSTART Startup time(2)

2. Startup times are crystal dependent. The crystal oscillator transconductance can be tuned to

compensate the variation of crystal oscillator series resistance.

VBAT=1.8 V, Fxo= 52

MHz 60 120 220 µs

Table 14. Ultra low power RC oscillator

Symbol Parameter Test conditions Min. Typ. Max. Unit

RCFCalibrated frequency

Calibrated RC oscillator

frequency is derived from

crystal oscillator frequency.

Digital clock domain 26 MHz -

34.7 kHz

RCTOL

Frequency accuracy after

calibration ±1 %

Table 15. N-Fractional Σ∆ frequency synthesizer characteristics

Symbol Parameter Test conditions Min. Typ. Max. Unit

FRES Frequency resolution Fxo = 26 MHz high band - 33 Hz

PNSYNTH

RF carrier phase noise

(915 MHz band)

10 kHz -100 -97 -94 dBc/Hz

100 kHz -104 -101 -99 dBc/Hz

200 kHz -105 -102 -100 dBc/Hz

500 kHz -112 -110 -107 dBc/Hz

1 MHz -120 -118 -116 dBc/Hz

2 MHz -123 -121 -119 dBc/Hz

TOTIME PLL turn-on/hop time 60 80 µs

CALTIME PLL calibration time 54 µs

DocID025109 Rev 1 21/70

STS1TX Characteristics

6.2.5 Sensors

Characteristics measured over recommended operating conditions unless otherwise

specified. All typical values are referred to TA = 25 °C, VBAT = 3.0 V.

Table 16. Analog temperature sensor characteristics

Symbol Parameter Test conditions Min. Typ. Max. Unit

TERR Error in temperature Across the temperature range

±2.5

°C

TSLOPE Temperature coefficient 2.5 mV/

°C

VTS-OUT Output voltage level 0.92 V

TICC Current consumption

Buffered output (low output

impedance; about 400 Ohm) 600 µA

Not buffered output (high output

impedance; about 100 kΩ)10 µA

Table 17. Battery indicator and low battery detector(1)

Symbol Parameter Test conditions Min. Typ. Max. Unit

VBLT Battery level thresholds 2.1 2.7 V

VBOT Brownout threshold

Measured in slow battery

variation (static) conditions

(inaccurate)

1.535 V

Measured in slow battery

variation (static) conditions

(accurate)

1.684 V

BOThyst Brownout threshold hysteresis 70 mV

1. For battery powered equipment, the TX does not transmit at incorrect frequencies under low battery voltage

conditions. It either remains on channel or stops transmitting. The latter can of course be implemented by

using a lock detect and/or by switching off the PA under control of the battery monitor. For testing purposes

this control is enabled/disabled by SPI.

Operating modes STS1TX

22/70 DocID025109 Rev 1

7 Operating modes

The STS1TX is equipped with a built-in main controller which controls the switching

between the two main operating modes: transmit (TX).

In shutdown condition (the STS1TX can be switched on/off with the external pin SDN, all

other functions/registers/commands are available through the SPI interface and GPIOs), no

internal supply is generated (in order to minimize battery leakage), and hence, all stored

data and configurations are lost. The GPIO and SPI ports during SHUTDOWN are in HiZ.

From shutdown, the STS1TX can be switched on from the SDN pin and goes into READY

state, which is the default, where the reference signal from XO is available.

From READY state, the STS1TX can be moved to LOCK state to generate the high

precision LO signal and/or TX mode. At the end of the operations above, the STS1TX can

return to its default state (READY) and can then be put into a sleep condition (SLEEP state),

with very low power consumption. If no timeout is required, the STS1TX can be moved from

READY to STANDBY state, which has the lowest possible current consumption while

retaining FIFO, status and configuration registers. To manage the transitions towards and

between these operating modes, the controller works as a state-machine, whose state

switching is driven by SPI commands. See Figure 4 for state diagram and transition time

between states.

Figure 4. Diagram and transition

The STS1TX radio control has three stable states (READY, STANDBY, LOCK) which may

be defined stable, and they are accessed by the specific commands (respectively READY,

STANDBY, and LOCKTX), which can be left only if any other command is used. All other

states are transient, which means that in a typical configuration, the controller remains in

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DocID025109 Rev 1 23/70

STS1TX Operating modes

those states, at most for any time-out timer duration. Also the READY and LOCK states

behave as transients when they are not directly accessed with the specific commands (for

example, when LOCK is temporarily used before reaching the TX state).

Note: Response time SHUTDOWN to READY is ~650 µs.

READY state is the default state after the power-on reset event. In the steady condition, the

XO is settled and usable as the time reference for RCO calibration, for frequency synthesis,

and as the system clock for the digital circuits.

The TX mode can be activated directly by the MCU using the TX command, or automatically

if the state machine wakes up from SLEEP mode and some previous TX is pending. The

values are intend to a VCO manual calibration.

In LOCK state the synthesizer is in a locking condition(a). If LOCK state is reached using

specific command LOCKTX, the state machine remains in LOCK state and waits for the

next command. This feature can be used by the MCU to perform preliminary calibrations, as

the MCU can read the calibration word in the RCO_VCO_CALIBR_OUT register and store it

in a non-volatile memory, and after that it requires a further tuning cycle.

When TX is activated by the TX command, the state machine goes into TX state and

remains there until the current packet is fully transmitted or, in the case of direct mode TX,

TXFIFO underflow condition is reached or the SABORT command is applied.

Table 18. States

STATE[6:0](1) State/mode Digital LDO SPI Xtal RF

Synth.

Wakeup

timer

Response time

to(2)

- SHUTDOWN OFF (register

contents lost) Off Off Off Off NA

0x40 STANDBY

ON (FIFO and

contents

retained)

On Off Off Off 125 µs

0x36 SLEEP On Off Off On 125 µs

0x03 READY

(Default) On On Off Don’t care 50 µs

0x0F LOCK On On On Don’t care NA

0x5f TX On On On Don’t care NA

1. All others values of STATE[6:0] are invalid and are an indication of an error condition due to bad registers

configuration and/or hardware issue in the application board hosting STS1TX.

2. These values are crystal dependent. The values are referred to 52 MHz.

a. LOCK state is reached when one of the following events occurs first: lock detector assertion or locking timeout

expiration.

Operating modes STS1TX

24/70 DocID025109 Rev 1

After TX completion, the possible destinations are:

•TX, if the persistent-TX option is enabled in the PROTOCOL configuration registers

•PROTOCOL, if some protocol option (e.g. automatic re-transmission) is enabled

•READY, if TX is completed and no protocol option is in progress.

The SABORT command can always be used in TX state to break any deadlock condition

and the subsequent destination depends on STS1TX programming according to the

description above.

Commands are used in the STS1TX to change the operating mode, to enable/disable

functions, and so on. A command is sent on the SPI interface and may be followed by any

other SPI access without pulling CSn high.

The complete list of commands is reported in Table 19. Note that the command code is the

second byte to be sent on the MOSI pin (the first byte must be 0x80).

The commands are immediately valid after SPI transfer completion (i.e. no need for any

CSn positive edge).

7.1 Reset sequence

The STS1TX includes an automatic power-on reset (POR) circuit which generates an

internal RESETN active (low) level for a time TRESET after the VDD reaches the reset

Table 19. Commands list

Command

code Command name Execution state Description

0x60 TX READY Start to transmit

0x62 READY STANDBY, SLEEP,

LOCK Go to READY

0x63 STANDBY READY Go to STANDBY

0x64 SLEEP READY Go to SLEEP

0x66 LOCKTX READY Go to LOCK state by using the TX configuration of the

synthesizer

0x67 SABORT TX Exit from TX state and go to READY state

0x68 LDC_RELOAD All Reload the LDC timer with the value stored in the

LDC_PRESCALER/COUNTER registers

0x69 SEQUENCE_UPDA

TE All Reload the packet sequence counter with the value

stored in the PROTOCOL[2] register.

0x6A AES Enc All Start the encryption routine

0x6B AES Key All Start the procedure to compute the key for decryption

0x6C AES Dec All Start decryption using the current key

0x6D AES KeyDec All Compute the key and start decryption

0x70 SRES All Reset

0x72 FLUSHTXFIFO All Clean the TX FIFO

RESET

DocID025109 Rev 1 25/70

STS1TX Operating modes

release threshold voltage VRRT (provided that SDN is low), as shown below. The same reset

pulse is generated after a step-down on the input pin SDN (provided that VDD>VRRT).

Figure 5. Power-on reset timing and limits

The parameters VRRT and TRESET are fixed by design. At RESET, all the registers are

initialized to their default values. Typical and extreme values are reported in the following

table.

Note: An SRES command is also available, which generates an internal RESET of the STS1TX.

7.2 Timer usage

Most of the timers are programmable via R/W registers. All timer registers are made up of

two bytes: the first byte is a multiplier factor (prescaler); the second byte is a counter value.

Note: If the counter register value (prescaler register value) is 0, the related timer never stops

(infinite timeout), despite the value written in the prescaler register (counter register).

The available timers and their features are listed in the following table.

Table 20. POR parameters

Symbol Parameter Min. Typ. Max. Unit

VRRT Reset startup threshold voltage 0.5 V

TRESET Reset pulse width 0.24 0.65 1.0 ms

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Timer period= PRESCALER x COUNTER x Tclk

Operating modes STS1TX

26/70 DocID025109 Rev 1

Note: It is not allowed to set LDC_PRESCALER or LDC_COUNTER to 0

For LDCR_COUNTER and LDCR_PRESCALER only, the effective number of cycles

counted is given by the value + 1 (e.g. counter=1 and prescaler=1 produces 2 x 2=4 counts,

counter=1 and prescaler=2 produces 2 x 3=6 counts, etc.).

Table 21. STS1TX timers description and duration

No. Register name Description Source Time

step Max. time

3 LDCR_PRESCALER

Wakeup period RCO ~29µs ~2s

4 LDCR_COUNTER

DocID025109 Rev 1 27/70

STS1TX Block description

8 Block description

8.1 Power management

The STS1TX integrates a high efficiency step-down converter cascaded with LDOs meant

to supply both analog and digital parts. However, an LDO directly fed by the external battery

provides a controlled voltage to the data interface block.

8.1.1 Switching frequency

The SMPS switching frequency can be provided either by a divider by four or by a

programmable rate multiplier. The divider by four or the rate multiplier is activated when the

EN_RM bit is set to both 0 and 1 in the PM_CONFIG[2:0] register bank. When the rate

multiplier is activated, the divider ratio can be programmed by KRM[14:0] word in the

PM_CONFIG[2:0] register bank. In this case, the SMPS switching frequency is given by the

following formula:

The SMPS runs properly when the bits SET_SMPS_VTUNE and SET_SMPS_PLLBW (see

PM_CONFIG[2:0] register bank) are set according to the programmed switching frequency.

8.2 Power-on-reset (POR)

The power-on-reset circuit generates a reset pulse upon power-up which is used to initialize

the entire digital logic. Power-on-reset senses VBAT voltage.

8.3 Low battery indicator

The battery indicator can provide the user with an indication of the battery voltage level.

There are two blocks to detect battery level:

•Brownout with a fixed threshold as defined inTable 17: Battery indicator and low battery

detector

•Battery level detector with a programmable threshold as defined in Table 17: Battery

indicator and low battery detector.

Table 22. SMPS configuration settings

SET_SMPS_PLLBW SET_SMPS_VTUNE Switching frequency range

0 0 2.0 MHz - 4.5 MHz

0 1 3.5 MHz - 7.0 MHz

1 0 4.5 MHz - 7.5 MHz

1 1 4.5 MHz - 10 MHz

Fsw

KRM fCLK

⋅

215

------------------------------=

Block description STS1TX

28/70 DocID025109 Rev 1

Both blocks can be optionally activated to provide the MCU with an early warning of

impending power failure. It does not reset the system, but gives the MCU time to prepare for

an orderly power-down and provides hardware protection of data stored in the program

memory, by preventing write instructions being executed.

The low battery indicator function is available in any of the STS1TX operating modes. As

this function requires the internal bias circuit operation, the overall current consumption in

STANDBY, SLEEP, and READY modes is increased by 400 µA.

8.4 Voltage reference

This block provides the precise reference voltage needed by the internal circuit.

8.5 Oscillator and RF synthesizer

A crystal connected to XIN and XOUT is used to provide a clock signal to the frequency

synthesizer. The allowed clock signal frequency is either 24, 26, 48, or 52 MHz. As an

alternative, an external clock signal can be used to feed XIN for proper operation. In this

option, XOUT can be left either floating or tied to ground.

Since the digital macro cannot be clocked at that double frequency (48 MHz or 52 MHz), a

divided clock is used in this case.

The digital clock divider is enabled by default and must be kept enabled if the crystal is in

the (48 - 52) MHz range; if the crystal is in the (24 - 26) MHz range, then the divider must be

disabled before starting any TX operation. The safest procedure to disable the divider

without any risk of glitches in the digital clock is to switch into STANDBY mode, thereby

resetting the bit-field PD_CLKDIV in the XO_RCO_TEST register, and then return to the

READY state. Also, the synthesizer reference signal can be divided by 2, setting the bit-field

REFDIV in the SYNTH_CONFIG register.

The integrated phase locked loop (PLL) is capable of synthesizing a wide band of

frequencies, in particular the bands from 150 to 174 MHz, from 300 to 348 MHz, from 387 to

470 MHz, or from 779 to 956 MHz, the input signal for the PA in the TX chain.

Frequency tolerance and startup times depend on the crystal used, although some tuning of

the latter parameter is possible through the GM_CONF field of the ANA_FUNC_CONF

registers.

Table 23. Programmability of trans-conductance at startup

GM_CONF[2:0] Gm at startup [mS]

000 13.2

001 18.2

010 21.5

011 25.6

100 28.8

101 33.9

DocID025109 Rev 1 29/70

STS1TX Block description

Depending on the RF frequency and channel spacing, a very high accurate crystal or TCXO

may be required.

The RF synthesizer implements fractional sigma delta architecture to allow fast settling and

narrow channel spacing. It is fully integrated and uses a multi-band VCO to cover the whole

frequency range. All internal calibrations are performed automatically.

The PLL output frequency can be configured by programming the SYNT field of the SYNT3,

SYNT2, SYNT1, and SYNT0 registers and BS field of the SYNT0 register. The user must

configure these registers according to the effective reference frequency in use (24 MHz, 26

MHz, 48 MHz, or 52 MHz). In the latter two cases, the user must enable the frequency

divider by 2 for the digital clock, in order to run the digital macro at a lower frequency. The

configuration bit for the digital clock divider is inside the XO_RCO_TEST register (default

case is divider enabled). In addition, the user can also enable a divider by 2 applied to the

reference clock. The configuration bit for the reference clock divider is inside the

SYNTH_CONFIG[1] register. The user must select a 3-bit word in order to set the charge

pump current according to the LO frequency variations, in order to have a constant loop

bandwidth. This can be done by writing the WCP field of the SYNT3 register, according to

the following table:

110 38.5

111 43.0

Table 24. CP word look-up

Channel frequency WCP [2:0]

145.1 147.1 000

147.1 149.1 001

149.1 151.1 010

151.1 153.2 011

153.2 155.2 100

155.2 157.2 101

157.2 159.2 110

159.2 161.1 111

161.3 163.5 000

163.5 165.7 001

165.7 168.0 010

168.0 170.3 011

170.3 172.5 100

172.5 174.8 101

174.8 177.0 110

177.0 179.3 111

Table 23. Programmability of trans-conductance at startup (continued)

GM_CONF[2:0] Gm at startup [mS]

Block description STS1TX

30/70 DocID025109 Rev 1

290.3 294 000

294.3 298.3 001

298.3 302.3 010

302.4 306.4 011

306.4 310.4 100

310.4 314.4 101

314.4 318.4 110

318.4 322.6 111

322.6 327.0 000

327.0 331.4 001

331.4 335.9 010

335.9 340.5 011

340.5 344.9 100

344.9 349.5 101

349.5 353.9 110

353.9 358.5 111

387.0 392.3 000

392.3 397.7 001

397.7 403.0 010

403.0 408.5 011

413.8 419.2 101

419.2 424.6 110

424.6 430.1 111

430.1 436.0 000

436.0 441.9 001

441.9 447.9 010

447.9 454.0 011

454.0 459.9 100

459.9 466.0 101

466.0 471.9 110

471.9 478.0 111

774.0 784.7 000

784.7 795.3 001

795.3 806.0 010

806.0 817.0 011

Table 24. CP word look-up (continued)

Channel frequency WCP [2:0]

DocID025109 Rev 1 31/70

STS1TX Block description

The STS1TX is provided with an automatic and very fast calibration procedure for the

frequency synthesizer. If not disabled, it is performed each time the SYNTH is required to

lock to the programmed RF channel frequency (i.e. from READY to LOCK/TX). Calibration

time is 54 µs.

After completion, the calibration word is used automatically by the STS1TX and is stored in

the RCO_VCO_CALIBR_OUT[1:0] registers.

In order to get the synthesizer locked when the calibration procedure is not enabled, the

correct calibration words to be used must be previously stored in the

RCO_VCO_CALIBR_IN[2:0] registers using VCO_CALIBR_TX field.

The advantage of performing an offline calibration is that the LOCK/setting time is roughly

20 µs (using proper VCO_CALIBR_TX register values).

It is recommended to set the T split time to the longest value (3.47 ns) to facilitate the

calibrator operation, SEL_TSPLIT field of the register SYNTH_CONFIG[0] (register address

0x9F) at 1.

If calibration is enabled, the LOCK/setting time is approximately 80 µs.

8.6 RCO: features and calibration

The STS1TX contains an ultra low-power RC oscillator capable of generating 34.7 kHz with

both 24 MHz and 26 MHz; the RC oscillator frequency is calibrated comparing it to the

digital domain clock fCLK divided by 692 or 750, respectively. The configuration bit, called

24_26MHz_SELECT in the ANA_FUNC_CONF register, contains the information of the

calibrator regarding the frequency of the crystal under operation. If the digital domain clock

is 25 MHz, the setting of the configuration bit 24_26MHz_SELECT will calibrate the low

power RC oscillator according to the following table:

817.0 827.7 100

827.7 838.3 101

838.3 849.2 110

849.2 860.2 111

860.2 872.0 000

872.0 883.8 001

883.8 895.8 010

908.0 919.8 100

919.8 932.0 101

932.0 943.8 110

943.8 956.0 111

Table 24. CP word look-up (continued)

Channel frequency WCP [2:0]

Block description STS1TX

32/70 DocID025109 Rev 1

By default, the calibration is disabled at reset to avoid using an out-of-range reference

frequency (for instance, when the XTAL is 26 MHz and the digital divider is active, in fact, by

default). After the internal clock divider is correctly configured, the user can enable the RCO

calibration in the PROTOCOL[2] register.

The user can replace the internal 34 kHz-signal source with an external one (provided

through a GPIO, Section 10.3). To enable the usage of the external signal, the user must set

the EXT_RCOSC bit in the XO_RCO_CONFIG register. However, the internal calibrator is

not automatically disabled from the EXT_RCOSC bit (the user must reset the

RCO_CALIBRATION bit in the PROTOCOL[2] register, if previously set).

8.6.1 RC oscillator calibration

RC oscillator calibration is enabled when bit RCO_CALIBRATION is set in the

PROTOCOL[2] register (by default the calibration is disabled). The calibration words found

by the calibration algorithm are accessible in the RCO_VCO_CALIBR_OUT[1:0] registers

(fields RWT_OUT[3:0] and RFB_OUT[4:0],).

When the calibration is disabled, the frequency of the RC oscillator is set by a couple of

configuration words, namely RWT_IN[3:0] and RFB_IN[4:0], in the

RCO_VCO_CALIBR_IN[2:0] registers (fields RWT_IN[3:0] and RFB_IN[4:0]). RWT_IN[3:0]

can range from 0 up to 13 (decimal value) affecting the raw value of the frequency, while the

more accurate and fine control is up to RFB_IN[4:0] (ranging from 1 up to 31).

8.7 Transmitter

The STS1TX contains an integrated PA capable of transmitting at output levels between -30

dBm to +11 dBm. The PA is single-ended and has a dedicated pin (TXOUT). The PA output

is ramped up and down to prevent unwanted spectral splatter. In TX mode the PA drives the

signal generated by the frequency synthesizer out to the antenna terminal. The output

power of the PA is programmable via SPI. Delivered power, as well as harmonic content,

depends on the external impedance seen by the PA. To obtain approval on ETSI EN 300

220, it is possible to program TX to send an unmodulated carrier.

The output stage is supplied from the SMPS through an external choke and is loaded with a

LC-type network which has the function of transforming the impedance of the antenna and

filter out the harmonics.

Table 25. RC calibrated speed

Digital domain clock 24_26MHz_SELECT RC calibrated speed

24 MHz 0 34.7 kHz

26 MHz 1 34.7 kHz

25 MHz 0 36.1 kHz

25 MHz 1 33.3 kHz

DocID025109 Rev 1 33/70

STS1TX Block description

Figure 6. Shaping of ASK signal

8.8 Temperature sensors (TS)

The STS1TX can provide an analog temperature indication as a voltage level, which is

available at the GPIO_0 pin. The voltage level V0 at room temperature (or any other useful

reference temperature) should be acquired and stored by the MCU in order to compensate

for the offset. The relationship between temperature and voltage is the following:

Equation 1

where V0 is the voltage at temperature T0.

Two output modes are available: buffered or not buffered (high output impedance, about

100 kΩ). The latter mode is the default.

The TS function is available in every operating mode. When enabled, the internal logic

allows the switching on of all the necessary circuitry.

To enable the TS function, the user must perform the following operations:

•Set to 1 the TS bit in the ANA_FUNC_CONF[0] register

•Program as “Analog” (00) the GPIO_MODE field in the GPIO0_CONF register (other

fields are neglected)

•Optionally, enable the buffered mode (the EN_TS_BUFFER bit in the PM_CONFIG[2]

As the TS function requires the internal bias circuit operation, the overall current

consumption in STANDBY, SLEEP, and READY modes is increased by 400 µA.

8.9 AES encryption co-processor

The STS1TX provides data security support as it embeds an advanced encryption standard

(AES) core which implements a cryptographic algorithm in compliance with NIST FIPS 197.

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Transmission and reception STS1TX

34/70 DocID025109 Rev 1

Three registers are available to use the AES engine of STS1TX:

•AES_KEY_IN [15:0]: R/W type register (128-bit), used to provide the key to use

•AES_DATA_IN [15:0]: R/W type register (128-bit), used to provide the input to the AES

engine

•AES_DATA_OUT [15:0]: R type register (128-bit), used to retrieve the output of the

AES operation.

The core processes 128-bit data blocks using 128-bit keys.

The AES can be accessed in any of the STS1TX operation modes.

To turn on the AES engine, the AES_ON bit in the ANA_FUNC_CONF[0] register must be

set.

Once the AES engine is on, it processes the operations according to the commands sent.

The STS1TX engine provides 4 different operations:

1. Encryption using a given encryption key (AES Enc command). In this operation, the

MCU puts the encryption key into the AES_KEY_IN[15:0] register and the data to

encrypt into the AES_DATA_IN[15:0]. The MCU sends the AES Enc command and

when the AES_EOP (end of operation) is issued, the MCU can retrieve the data

encrypted from AES_DATA_OUT[15:0]

2. Decryption key derivation starting from an encryption key (AES Key command). In this

operation, the MCU puts the encryption key into AES_DATA_IN[15:0]. The MCU sends

the AES Key command and when the AES_EOP (end of operation) is issued, the MCU

can retrieve the decryption key from AES_DATA_OUT[15:0]

3. Data decryption using a decryption key (AES Dec command). In this operation, the

MCU puts the decryption key into the AES_KEY_IN[15:0] register and the data to

decrypt into AES_DATA_IN[15:0]. The MCU sends the AES Dec command and when

the AES_EOP (end of operation) is issued, the MCU can retrieve the data decrypted

from AES_DATA_OUT[15:0].

4. Data decryption using a decryption key (AES KeyDec command). In this operation, the

MCU puts the encryption key into the AES_KEY_IN[15:0] register and the data to

decrypt into AES_DATA_IN[15:0]. The MCU sends the AES KeyDec command and

when the AES_EOP (end of operation) is issued, the MCU can retrieve the data

decrypted from AES_DATA_OUT[15:0].

9 Transmission and reception

9.1 PA configuration

The PA output power level can be configured by programming the PA_POWER[8:0] register

bank. The user can store up to eight output levels to provide flexible PA power ramp-up and

ramp-down at the start and end of a frequency modulation transmission as well as ASK

modulation shaping.

The power levels of the ramp are controlled by 7-bit words (PA_LEVEL_x, x=0 − 7),

according to the following table:

DocID025109 Rev 1 35/70

STS1TX Transmission and reception

The power ramping is enabled by the PA_RAMP_ENABLE bit. If enabled, the ramp starts

from the level defined by the word PA_LEVEL_0 and stops at the level defined by the word

PA_LEVEL_x, where x is the value of the 3-bit field PA_LEVEL_MAX_INDEX. So, a

maximum of 8 steps can be set up. Figure 7 describes the levels table and shows some

examples.

Each step is held for a time interval defined by the 2-bit field PA_RAMP_STEP_WIDTH. The

step width is expressed in terms of bit period units (Tb/8), maximum value is 3 (which means

4×Tb/8=Tb/2). Therefore the PA ramp may last up to 4 Tb (about 3.3 ms if the bit rate is 1.2

kbit/s).

Table 26. PA_level

PA_LEVEL_x Comment POUT [dBm]

(170MHz)

0No output power: output stage in high impedance

mode and all circuits switched off. -

1 Maximum output power 11

…

30 0

…

42 -6

…

90 Minimum level -34

91-127 Reserved N/A

Transmission and reception STS1TX

36/70 DocID025109 Rev 1

Figure 7. Output power ramping configuration

The set of 8 levels is used to shape the ASK signal. In this case, the modulator works as a

counter that counts up when transmitting a one and down when transmitting a zero. The

counter counts at a rate equal to 8 times the symbol rate (in this case, the field

PA_RAMP_STEP_WIDTH is not used). This counter value is used as an index for the

lookup in the levels table in Figure 7 to associate the relevant POUT value. Therefore, in

order to utilize the whole table, PA_LEVEL_MAX_INDEX should be 7 when ASK is active.

The real shaping of the ASK signal is dependent on the configuration of the PA_LEVEL_x

registers. Figure 7 shows some examples of ASK shaping.

Using the a frequency modulation, the output power is configured by PA_LEVEL_x, with

x=PA_LEVEL_MAX_INDEX.

For OOK modulation, the signal is abruptly switched between two levels only, these are

PA_LEVEL_0 and PA_LEVEL_x, with x=PA_LEVEL_MAX_INDEX.

The 2-bit CWC field in the PA_POWER register bank can be used to tune the internal

capacitive load of the PA (up to 3.6 pF in steps of 1.2 pF) in order to optimize the

performance at different frequencies.

The output power are reported in Table 26: PA_level.

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DocID025109 Rev 1 37/70

STS1TX Transmission and reception

9.2 RF channel frequency settings

RF channels can be defined using the CHSPACE and CHNUM registers.

The channel center frequency can be programmed as:

Equation 2

This allows the setting of up to 256 channels with a programmable raster. The raster

granularity is about 793 Hz at 26 MHz and becomes about 1587 Hz at 52 MHz.

The actual channel spacing is from 793 Hz to 202342 Hz in 793 Hz steps for the 26 MHz

configuration and from 1587 to 404685 Hz in 1587 Hz steps for the 52 MHz configuration.

The base carrier frequency, i.e. the carrier frequency of channel #0, is controlled by the

SYNT0, SYNT1, SYNT2, and SYNT3 registers according to the following formula:

Equation 3

where:

•fXO is the frequency of the XTAL oscillator (typically 24 MHz, 26 MHz, 48 MHz, or 52

MHz)

•SYNT is a programmable 26-bit integer.

Equation 4

Equation 5

The offset frequency is a correction term which can be set to compensate the crystal

inaccuracy after e.g. lab calibration.

Equation 6

CHNUMCHSPACE

fff 15

offsetbasec ⋅













⋅++=

base 2

SYNT

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2 if REFDIV 1 (internal reference divider is enabled)







OFFSET_FC

f18

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Transmission and reception STS1TX

38/70 DocID025109 Rev 1

where:

•FC_OFFSET is a 12-bit integer (expressed as 2's complement number) set by the

FC_OFFSET[1:0] registers

Furthermore, the selection between VCOH (“high”) and VCOL (“low”) in the frequency

synthesizer according to the band selected and the VCO threshold is required.

If the center frequency is below the frequency threshold for that frequency band, the VCO_L

must be selected by setting the bit 2 VCO_L_SEL field in the SYNTH_CONFIG register.

If the center frequency is above the frequency threshold for that frequency band, VCO_H

must be selected by setting the bit 1 VCO_ H _SEL field in the SYNTH_CONFIG register.

The user must make sure that actual frequency programming is inside the specified

frequency range. The accuracy of the offset is about 99 Hz for the 26 MHz reference and

about 198 Hz for the 52 MHz reference.

9.3 Modulation scheme

The following modulation formats are supported: 2-FSK, GFSK, MSK, OOK, and ASK. The

actual modulation format used is controlled by the MOD_TYPE field of the MOD0 register:

•MOD_TYPE =

– 0 (00): 2-FSK

– 1 (01): GFSK

– 2 (10): ASK/OOK

– 3 (11): MSK

In 2-FSK and GFSK modes, the frequency deviation is controlled by the FDEV register

according to the following formula:

Equation 7

where:

•fXO is the XTAL oscillator frequency (typically 26 MHz or 52 MHz).

•FDEV_M is a 3-bit integer ranging from 0 to 7

•FDEV_E is a 4-bit integer ranging from 0 to 9.

The fdev values obtainable are then:

For fXO = 52 MHz

Table 27. Frequency threshold

Frequency threshold for each band (MHz)(1)

1. By default, the VCO_H is selected.

Very low band Low band Middle band High band

161281250 322562500 430083334 860166667

fdev fxo

floor 8(( FDEV_M )+2FDEV_E 1–)⋅

218

--------------------------------------------------------------------------------------------

DocID025109 Rev 1 39/70

STS1TX Transmission and reception

For fXO = 26 MHz

With this solution the maximum deviation for the 26 MHz case is limited to about 355 kHz,

but this is still acceptable since the maximum useful deviation is about 125 kHz (MSK @

500 kbps).

In GFSK mode the Gaussian filter BT product can be set to 1 or 0.5 by the field BT_SEL of

the MOD0 register.

In MSK mode, the frequency deviation is automatically set to ¼ of the data rate and the

content of the FDEV register is ignored.

The calculation done within the modem assumes that the digital clock is equal to the

synthesizer reference. Hence, in the 52-MHz case the MSK can actually be configured by

setting the frequency deviation to ¼ of the data rate through the FDEV registers as for

normal 2-FSK. The same is true for GMSK mode, which can be configured by setting the

frequency deviation to ¼ of the data rate through the FDEV registers as for normal GFSK

with Gaussian filter BT equal to 1 or 0.5.

E/M01234567

0 793.5 793.5 991.8 991.8 1190.2 1190.2 1388.5 1388.5

1 1586.9 1785.3 1983.6 2182.0 2380.4 2578.7 2777.1 2975.5

2 3173.8 3570.6 3967.3 4364.0 4760.7 5157.5 5554.2 5950.9

3 6347.7 7141.1 7934.6 8728.0 9521.5 10314.9 11108.4 11901.9

4 12695.3 14282.2 15869.1 17456.1 19043.0 20629.9 22216.8 23803.7

5 25390.6 28564.5 31738.3 34912.1 38085.9 41259.8 44433.6 47607.4

6 50781.3 57128.9 63476.6 69824.2 76171.9 82519.5 88867.2 95214.8

7 101562.5 114257.8 126953.1 139648.4 152343.8 165039.1 177734.4 190429.7

8 203125.0 228515.6 253906.3 279296.9 304687.5 330078.1 355468.8 380859.4

9 406250.0 457031.3 507812.5 558593.8 609375.0 660156.3 710937.5 761718.8

E/M01234567

0 396.7 396.7 495.9 495.9 595.1 595.1 694.3 694.3

1 793.5 892.6 991.8 1091.0 1190.2 1289.4 1388.5 1487.7

2 1586.9 1785.3 1983.6 2182.0 2380.4 2578.7 2777.1 2975.5

3 3173.8 3570.6 3967.3 4364.0 4760.7 5157.5 5554.2 5950.9

4 6347.7 7141.1 7934.6 8728.0 9521.5 10314.9 11108.4 11901.9

5 12695.3 14282.2 15869.1 17456.1 19043.0 20629.9 22216.8 23803.7

6 25390.6 28564.5 31738.3 34912.1 38085.9 41259.8 44433.6 47607.4

7 50781.3 57128.9 63476.6 69824.2 76171.9 82519.5 88867.2 95214.8

8 101562.5 114257.8 126953.1 139648.4 152343.8 165039.1 177734.4 190429.7

9 203125.0 228515.6 253906.3 279296.9 304687.5 330078.1 355468.8 380859.4

Transmission and reception STS1TX

40/70 DocID025109 Rev 1

OOK and ASK

If MOD_TYPE = 2 and power ramping is enabled, then ASK is used; otherwise, if

MOD_TYPE = 2 and power ramping is disabled, then OOK is used.

When OOK is selected, a bit '1' is transmitted with the power specified by

PA_POWER[PA_LEVEL_MAX_INDEX], a bit '0' is transmitted with the power specified by

PA_POWER[0](normally set to PA off).

When ASK is selected, a bit '1' is transmitted with a power ramp increasing from

PA_POWER[0] to PA_POWER[PA_LEVEL_MAX_INDEX], a bit '0' is transmitted with a

power ramp decreasing from PA_POWER[PA_LEVEL_MAX_INDEX] to PA_POWER[0].

The duration of each power step is 1/8 of the symbol time.

If more '1's are transmitted consecutively, the PA power remains at

PA_POWER[PA_LEVEL_MAX_INDEX] for all '1's following the first one; If more '0's are

transmitted consecutively, the PA power remains at PA_POWER[0] for all '0's following the

first one.

CW mode

For test and measurement purposes the device can be programmed to generate a

continuous wave carrier without any modulation by setting the CW field of the MOD0

transmitter in TX state for an undefined period of time.

9.3.1 Data rate

The data rate is controlled by the MOD0 and MOD1 registers according to the following

formula:

Equation 8

where:

•DATARATE_M is an 8-bit integer ranging from 0 to 255

•DATARATE_E is a 4-bit integer ranging from 0 to 15

•fclk is the digital clock frequency (typically 26 MHz).

The minimum data rate at fclk = 26 MHz is about 25 Hz; the maximum data rate is about 1.6

MHz. Be advised that performance for such values is not guaranteed.

9.4 Data coding and integrity check process

9.4.1 FEC

The device provides hardware support for error correction and detection.

Error correction can be either enabled or disabled according to link reliability and power

consumption needs. Convolutional coding with a rate=½ and k=4 is applied on the payload

and CRC before transmission (poly [13,17]).

DataRate fclk

256 DATA_RATE_M+()2DATARATE_E

⋅

228

-------------------------------------------------------------------------------------------------------⋅=

DocID025109 Rev 1 41/70

STS1TX Transmission and reception

To further improve error correction performance, a data interleaver is used when

convolutional coding is enabled. Data interleaving/de-interleaving is performed using a 4x4-

bit matrix interleaver.

To fill the entire matrix, at least 2 bytes of data payload are required (16 cells). In the

interleaver matrix, the encoded data bits are written along the rows and the sequence to

send to the modulator is obtained by reading the matrix elements along the columns of the

matrix. Due to the size of the matrix, the overall data transmitted must be an exact integer

multiple of two, to fill the rows and columns of the matrix. If necessary, the framer is able to

add automatically extra bytes at the end of the packet, so the number of bytes is an number.

FEC and interleaving are enabled/disabled together.

To enable FEC/INTERL, the field FEC_EN of PCKTCTRL1 must be set to ‘1’. When

FEC/INTERL is enabled, the number of transmitted bits is roughly doubled, hence the on-air

packet duration in time is roughly doubled as well. The data rate specified in Section 9.3.1

always applies to the on-air transmitted data.

A termination byte is automatically appended to set the encoder to the 0-state at the end of

the packet.

9.4.2 CRC

Error detection is implemented by means of cyclic redundancy check codes.

The length of the checksum is programmable to 8, 16, or 24 bits.

The CRC can be added at the end of the packet by the field CRC_MODE of the register

PCKCTRL1.

The following standard CRC polynomials can be selected:

•CRC mode = 1, 8 bits: the poly is (0x07) X8+X2+X+1

•CRC mode = 2, 16 bits: the poly is (0x8005) X16+X15+X2+1

•CRC mode = 3, 16 bits: the poly is (0x1021) X16+X12+X5+1

•CRC mode = 4, 24 bits: the poly is (0x864CFB)

X24+X23+X18+X17+X14+X11+X10+X7+X6+X5+X4+X3+X+1

•CRC is calculated over all fields excluding preamble and SYNC word.

9.4.3 Data whitening

To prevent short repeating sequences (e.g., runs of 0’s or 1’s) that create spectral lines,

which may complicate symbol tracking at the receiver or interfere with other transmissions,

the device implements a data whitening feature. Data whitening can be optionally enabled

by setting the filed WHIT_EN of the PCKTCTRL1 register to '1'. Data whitening is

implemented by a maximum length LFSR generating a pseudo-random binary sequence

used to XOR data before entering the encoding chain. The length of the LSFR is set to 9

bits. The pseudo-random sequence is initialized to all 1's.

Data whitening, if enabled, is applied on all fields excluding the preamble and the SYNC

words.

Whitening is applied according to the following LFSR implementation:

Transmission and reception STS1TX

42/70 DocID025109 Rev 1

Figure 8. LFSR block diagram

It is recommended to always enable data whitening.

9.4.4 Data padding

If FEC is enabled then the total length of payload and CRC must be an even number (in

order to completely fill up the interleaver). If not, a proper filling byte is automatically inserted

in transmission and removed by the receiver. The total packet length is affected, and it is

configured automatically enabling the FEC.

9.5 Packet handler engine

Before on-the-air transmission, raw data is properly cast into a packet structure. The

STS1TX offers a highly flexible and fully programmable packet; the structure of the packet,

the number, the type, and the dimension of the fields inside the packet depend on one of the

possible configuration settings. Through a suitable register the user can choose the packet

configuration from three options: STack, WM-Bus, and Basic.

The current packet format is set by the PCK_FRMT field of the PCKTCTRL3 register. In

particular:

•0 Basic packet format

•2 MBUS packet format

•3 STack packet format.

The general packet parameters which can be set by the user are listed and described

hereafter. Some particular restrictions are possible depending on the selected packet

format.

9.5.1 STack packet

AM03940v1

Tout

1-32 1-4 0-16 bit 1 1 0-4 2 bit 1 bit 0-65535 0-3

Preambl

eSync Length Dest.

address

Source

address Control Seq. No. NO_ACK Payload CRC

DocID025109 Rev 1 43/70

STS1TX Transmission and reception

Preamble (programmable field): the length of the preamble is programmable from 1 to 32

bytes by the PREAMBLE_LENGTH field of the PCKTCTRL2 register. Each preamble byte is

a '10101010' binary sequence.

Sync (programmable field): the length of the synchronization field is programmable (from 1

to 4 bytes) through dedicated registers. The SYNC word is programmable through registers

SYNC1, SYNC2, SYNC3, and SYNC4. If the programmed sync length is 1 then only the

SYNC1 word is transmitted; if the programmed sync length is 2 then only SYNC1 and

SYNC2 words are transmitted and so on.

Length (programmable/optional field): the packet length field is an optional field that is

defined as the cumulative length of Address (2 bytes always), Control, and Payload fields. It

is possible to support fixed and variable packet length. In fixed mode, the field length is not

used.

Destination address (programmable/optional field): is filled with the value of register

TX_DEST_ADDR.

Source address (programmable field): is filled with the value of register

TX_SOURCE_ADDR. The field ADDRESS_LEN of the PCKTCTRL4 register must be set

always to 2.

Control (programmable/optional field): is programmable from 0 to 4 bytes through the

CONTROL_LEN field of the PCKTCTRL4 register. Control fields of the packet can be set

using the TX_CTRL_FIELD[3:0] register.

Sequence number (programmable field): is a 2-bit field and contains the sequence number

of the transmitted packet. It is incremented automatically every time a new packet is

transmitted. It can be re-loaded with the value in the TX_SEQ_NUM_RELOAD[1:0] field of

the PROTOCOL[2] register, by using the SEQUENCE_UPDATE command.

NO_ACK (programmable field): It is programmed by the bit field NACK_TX of the register

PROTOCOL[0]. It is important set to 0 the bit field in the others packet formats.

Payload (programmable/optional field): the device supports both fixed and variable payload

length transmission from 0 to 65535 bytes.

On the transmitter, the payload length is always set as: PCKTLEN1 × 256 + PCKTLEN0.

In variable length mode, the width of the binary field transmitted, where the actual length of

payload is written, can be configured through the field LEN_WIDTH of the PCKTCTRL3

Example 1

•If the variable payload length is from 0 to 31 bytes, then LEN_WIDTH = 5

•If the variable payload length is from 0 to 255 bytes, then LEN_WIDTH = 8

•If the variable payload length is from 0 to 65535 bytes, then LEN_WIDTH = 16.

CRC (programmable/optional field): There are different polynomials CRC: 8 bits, 16 bits (2

polynomials are available) and 24 bits.

Transmission and reception STS1TX

44/70 DocID025109 Rev 1

9.5.2 Wireless M-Bus packet (W M-BUS, EN13757-4)

The WM-BUS packet structure is shown in the figure below (refer to EN13757 for details

about sub-mode specific radio setting).

The preamble consists of a number of chip sequences '01' whose length depends on the

chosen sub-mode according to EN13757-4. The length can be programmed using the

MBUS_PRMBL_CTRL, from a minimum to a maximum dictated from the standard

specification.

1st block, 2nd block, and optional blocks: can be defined by the user. The packet handler

engine uses the Manchester or the “3 out of 6” encoding for all the blocks according to the

defined sub-mode.

The postamble consists of a number of chip sequences '01' whose length depends on the

chosen sub-mode according to EN13757-4. The length can be programmed using the

MBUS_PSTMBL_CTRL, from a minimum to a maximum dictated from the standard

specification.

The sub-mode can be chosen setting the MBUS_SUBMODE[2:0] field of the MBUS_CTRL

•Submode S1, S2 (long header) (MBUS_SUBMODE=0):

– Header length = MBUS_PRMBL_CTRL + 279 (in '01' bit pairs)

– Sync word = 0x7696 (length 18 bits)

•Submode S1-m, S2, T2 (other to meter) (MBUS_SUBMODE =1):

– Header length = MBUS_PRMBL_CTRL + 15 (in '01' bit pairs)

– Sync word = 0x7696 (length 18 bits)

•Submode T1, T2 (meter to other) (MBUS_SUBMODE =3):

– Header length = MBUS_PRMBL_CTRL + 19 (in '01' bit pairs)

– Sync word = 0x3D (length 10 bits)

•Submode R2, short header (MBUS_SUBMODE =5):

– Header length = MBUS_PRMBL_CTRL + 39 (in '01' bit pairs)

– Sync word = 0x7696 (length 18 bits).

•Submode N1, N2, short header:

– Header length = 8 (in '01' bit pairs)

– Sync word = 0xF68D (length 18 bits).

9.5.3 Basic packet

Bytes nx(01) nx(01)

Preamble Sync 1st block 2nd block Opt. blocks Postamble

Manchester or 3 out of 6 encoding

1-32 1-4 0-16 bit 0-1 0-4 0-65535 0-3

Preamble Sync Length Address Control Payload CRC

DocID025109 Rev 1 45/70

STS1TX Transmission and reception

Preamble (programmable field): the length of the preamble is programmable from 1 to 32

bytes by the PREAMBLE_LENGTH field of the PCKTCTRL2 register. Each preamble byte is

a '10101010' binary sequence.

Sync (programmable field): the length of the synchronization field is programmable (from 1

to 4 bytes) through dedicated registers. The SYNC word is programmable through registers

SYNC1, SYNC2, SYNC3, and SYNC4. If the programmed sync length is 1, then only SYNC

word is transmitted; if the programmed sync length is 2 then only SYNC1 and SYNC2 words

are transmitted and so on.

Length (programmable/optional field): the packet length field is an optional field that is

defined as the cumulative length of Address, Control, and Payload fields. It is possible to

support fixed and variable packet length. In fixed mode, the field length is not used.

Destination address (programmable/optional field): is filled with the value of register

TX_DEST_ADDR.

Control (programmable/optional field): is programmable from 0 to 4 bytes through the

CONTROL_LEN field of the PCKTCTRL4 register. Control fields of the packet can be set

using the TX_CTRL_FIELD[3:0] register.

Payload (programmable/optional field): the device supports both fixed and variable payload

length transmission from 0 to 65535 bytes.

On the transmitter, the payload length is always set as: PCKTLEN1 × 256 + PCKTLEN0.

On the receiver, if the field FIX_VAR_LEN of PCKTCTRL2 register is set to 1, the payload

length is directly extracted from the received packet itself; if FIX_VAR_LEN is set to 0, the

payload length is controlled by the PCKTLEN0 and PCKTLEN1 registers as the transmitter.

Furthermore, in variable length mode, the width of the binary field transmitted, where the

actual length of payload is written, must be configured through the field LEN_WIDTH of the

PCKTCTRL3 register according to the maximum length expected in the specific application.

Example 1

•If the variable payload length is from 0 to 31 bytes, then LEN_WIDTH = 5

•If the variable payload length is from 0 to 255 bytes, then LEN_WIDTH = 8

•If the variable payload length is from 0 to 65535 bytes, then LEN_WIDTH = 16.

CRC (programmable/optional field): There are different polynomials CRC: 8 bits, 16 bits (2

polynomials are available) and 24 bits.

9.6 Data modes

Direct modes are primarily intended to completely bypass all the framer/deframer

operations, in order to give the user maximum flexibility in the choice of frame formats,

controlled by the field TXSOURCE of the PCKTCTRL1 register. In particular:

TXSOURCE =

•0 - normal modes

•1 - direct through FIFO: the packet is written in TX FIFO. The user build the packet

according to his need including preamble, payload and soon on. The data are

transmitted without any processing.

•2 - direct through GPIO: the packet bits are continuously read from one of the GPIO

pins, properly configured, and transmitted without any processing. To allow the

Transmission and reception STS1TX

46/70 DocID025109 Rev 1

synchronization of an external data source, a data clock signal is also provided on one

of the GPIO pins. Data are sampled by the device on the rising edge of such clock

signal; it is the responsibility of the external data source to provide a stable input at this

edge.

•3 - PN9 mode: a pseudo-random binary sequence is generated internally. This mode is

provided for test purposes only.

9.7 Data FIFO

In the STS1TX there is a TX FIFO for data to be transmitted, which is 96 bytes in length.

The SPI interface is used to write to the TX FIFO (see Figure 9) starting from the address

0xFF.

Figure 9. Threshold of the linear FIFO

The FIFO has two programmable thresholds: FIFO almost full and FIFO almost empty.

The FIFO almost full event occurs when the data crosses the threshold from below to

above. The TX FIFO almost empty threshold can be configured using the field TXAETHR in

the FIFO_CONFIG[0] register.

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DocID025109 Rev 1 47/70

STS1TX Transmission and reception

The FIFO almost empty event occurs when the data crosses the threshold from above to

below. The TX FIFO almost full threshold can be configured using the field TXAFTHR in the

FIFO_CONFIG[1] register.

Another event occurs when the FIFO goes into overflow or underflow.

The overflow happens when the data in the FIFO are more than 96 bytes. The underflow

happens when the STS1TX accesses the FIFO locations to read data, but there is no data

present.

For example:

•If it sends more data than the actual number of bytes in the TX FIFO, the TX FIFO

underflow/overflow error occurs for an underflow event.

•If it writes more than 96 bytes in the TX FIFO, a TX FIFO underflow/overflow error

occurs for an overflow event.

An easy way to clean the FIFOs is to use the flush command: FLUSHTXFIFO

The write TX FIFO operation needs an extra SPI transaction to write correctly the last byte

into the TX FIFO. Usually, this last SPI transaction is generated from the TX command sent

to transmit the data, otherwise a dummy SPI transaction must be done.

Using the auto-retransmission feature of the STS1TX (packet format STack), if the packet is

more than 96 bytes, the packet must be reloaded into the TX FIFO by the MCU. However, if

the payload is 96 bytes or less, the STS1TX handles the payload and it is not necessary to

reload the data into the TX FIFO at each retransmission.

9.8 Frequency hopping

In order to ensure good link reliability in an interference corrupted scenario, the device

supports frequency hopping, managed by the MCU; in particular, the STS1TX supports slow

frequency hopping, meaning that the systems change frequency at a rate slower than the

information rate.

Depending on the desired blanking interval (the time during a hop), frequency hopping can

be done by performing the complete PLL calibration for each channel hop, or reading in the

suitable register calibration data calculated at startup and stored in the non-volatile memory

of the MCU. The former solution gives a long blanking interval but is more robust compared

with supply voltage and temperature variation. The latter provides a shorter blanking time

but is sensitive to voltage and temperature variation and requires memory space to store

calibration data for each channel involved in hopping.

MCU interface STS1TX

48/70 DocID025109 Rev 1

10 MCU interface

Communication with the MCU goes through a standard 4-wire SPI interface and 4 GPIOs.

The device is able to provide a system clock signal to the MCU.

MCU performs the following operations:

•Program the STS1TX in different operating modes by sending commands

•Read and write buffered data, and status information from the SPI

•Get interrupt requests from the GPIO pins

•Apply external signals to the GPIO pins

10.1 Serial peripheral interface

The STS1TX is configured by a 4-wire SPI-compatible interface (CSn, SCLK, MOSI, and

MISO). More specifically:

•CSn: chip select, active low

•SCLK: bit clock

•MOSI: data from MCU to STS1TX (STS1TX is the slave)

•MISO: data from STS1TX to MCU (MCU is the master).

As the MCU is the master, it always drives the CSn and SCLK. According to the active

SCLK polarity and phase, the STS1TX SPI can be classified as mode 1 (CPOL=0,

CPHA=0), which means that the base value of SCLK is zero, data are read on the clock’s

rising edge and data are changed on the clock's falling edge. The MISO is in tri-state mode

when CSn is high. All transfers are done most significant bit first.

The SPI can be used to perform the following operations:

•Write data (to registers or FIFO queue)

•Read data (from registers or FIFO queue)

•Write commands.

The SPI communication is supported in all the active states, and also during the low power

state: STANDBY and SLEEP (see Table 18: States).

When accessing the SPI interface, the two status bytes of the MC_STATE[1:0] registers are

sent to the MISO pin. The timing diagrams of the three operations above are reported

below.

DocID025109 Rev 1 49/70

STS1TX MCU interface

Figure 10. SPI “write” operation

Figure 11. SPI “read” operation

Figure 12. SPI “command” operation

Concerning the first byte, the MSB is an A/C bit (Address/Commands: 0 indicates that the

following byte is an address, 1 indicates that the following byte is a command code), while

the LSB is a W/R bit (Write/Read: 1 indicates a read operation). All other bits must be zero.

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MCU interface STS1TX

50/70 DocID025109 Rev 1

Read and write operations are persistently executed while CSn is kept active (low), the

address being automatically incremented (burst mode).

Accessing the FIFO is done as usual with the read and write commands, by putting, as the

address, the code 0xFF. Burst mode is available to access the sequence of bytes in the

FIFO. Clearly, TX-FIFO with a write operation.

Details of the SPI parameters are reported below.

10.2 Interrupts

In order to notify the MCU of a certain number of events an interrupt signal is generated on

a selectable GPIO. The following events trigger an interrupt to the MCU:

Table 28. SPI interface timing requirements

Symbol Parameter Min. Max. Unit

fSCLK SCLK frequency 10 MHz

tsp CSn low to positive edge on SCLK 2 µs

Table 29. Interrupts

Bit Events group Interrupt event

Packet oriented

Not used

1 Not used

2TX data sent

3 Not used

4 Not used

5 TX FIFO underflow/overflow error

6 Not used

7 TX FIFO almost full

8 TX FIFO almost empty

9 Not used

10 Not used

11 Not used

Signal quality related

Not used

13 Not used

14 Not used

DocID025109 Rev 1 51/70

STS1TX MCU interface

All interrupts are reported on a set of interrupt status registers and are individually

maskable. The interrupt status register must be cleared upon a read event from the MCU.

The status of all the interrupts is reported on the IRQ_STATUS[3:0] registers: bits are high

for the events that have generated any interrupts. The interrupts are individually maskable

using the IRQ_MASK[3:0] registers: if the mask bit related to a particular event is

programmed at 0, that event does not generate any interrupt request.

10.3 GPIOs

The total number of GPIO pins is 4. Each pin is individually configurable.

Digital outputs can be selected from the following (see GPIOx_CONF register):

Device status related

Not used

16 READY(1)

17 STANDBY state switching in progress

18 Low battery level

19 Power-on reset

20 Brownout event

21 LOCK

Others

Not used

30 AES end–of–operation

1. The interrupt flag n.16 is set each time the STS1TX goes to READY state and the XO has

completed its setting transient (XO ready condition detected).

Table 29. Interrupts (continued)

Bit Events group Interrupt event

Table 30. Digital outputs

I/O selection Output signal

0 nIRQ (interrupt request, active low)

1 POR inverted (active low)

2 Wakeup timer expiration: ‘1’ when WUT has expired

3 Low battery detection: ‘1’ when battery is below threshold setting

4 TX data internal clock output (TX data are sampled on the rising edge of it)

5 TX state indication: ‘1’ when the STS1TX is transiting in the TX state

6 TX FIFO almost empty flag

7 TX FIFO almost full flag

8 Not used

9 Not used

10 Not used

MCU interface STS1TX

52/70 DocID025109 Rev 1

All interrupts are reported on a set of interrupt status registers and are individually

maskable. The interrupt status register must be cleared upon a read event from the MCU.

The status of all the interrupts is reported on the IRQ_STATUS[3:0] registers: bits are high

for the events that have generated any interrupts. The interrupts are individually maskable

using the IRQ_MASK[3:0] registers: if the mask bit related to a particular event is

programmed at 0, that event does not generate any interrupt request.

Digital inputs can be selected from the following (see GPIOx_CONF register):

11 Not used

12 Not used

13 Not used

14 Not used

15 Not used

16 Not used

17 Not used

18 TX mode indicator (to enable an external range extender)

19 VDD (to emulate an additional GPIO of the MCU, programmable by SPI)

20 GND (to emulate an additional GPIO of the MCU, programmable by SPI)

21 External SMPS enable signal (active high)

22 Device in SLEEP or STANDBY states

23 Device in READY state

24 Device in LOCK state

25 Device waiting for a high level of the lock-detector output signal

26 Device waiting for timer expiration before starting to sample the lock-detector output

signal

27 Device waiting for a high level of the READY2 signal from XO

28 Device waiting for timer expiration to allow PM block settling

29 Device waiting for end of VCO calibration

30 Device enables the full circuitry of the SYNTH block

31 Device waiting for a high level of the RCCAL_OK signal from the RCO calibrator

Table 31. Digital inputs

I/O selection Input signal

0 1 >> TX command

1 Not used

2 TX data input for direct modulation

Table 30. Digital outputs (continued)

I/O selection Output signal

DocID025109 Rev 1 53/70

STS1TX MCU interface

The only available analog output is the temperature sensor, see Section 8.8.

10.4 MCU clock

The STS1TX can directly provide the system clock to the MCU in order to avoid the need for

an additional crystal. The clock signals for the MCU can be available on the GPIO pins. The

source oscillator can be the internal RCO or the XO depending on the active state. When

XO is active, it is the source clock (the RCO is not available in this condition).

In addition, different ratios are available and programmable through the MCU_CK_CONF

configuration register, as described in Table 32.

3 Wakeup from external input (sensor output)

4 External clock @ 34.7 kHz (used for LDC modes timing)

From 5 to 31 Not used

Table 31. Digital inputs (continued)

I/O selection Input signal

Table 32. MCU_CK_CONF configuration register

MCU_CK_CONF[4:0]

Clock source Division ratio

XO_RATIO RCO_RATIO

Don’t care 0 RCO 1

1 1/128

0 Don’t care XO 1

12/3

21/2

31/3

41/4

51/6

61/8

71/12

81/16

91/24

10 1/36

11 1/48

12 1/64

13 1/96

14 1/128

15 1/192

MCU interface STS1TX

54/70 DocID025109 Rev 1

In STANDBY state, no oscillator is available as the clock source. In order to allow the MCU

to better handle this event, and avoid a potential dead state situation, a dedicated procedure

is forecast when the STS1TX enters STANDBY state. A few extra clock cycles can be

provided to the MCU before actually stopping the clock (an interrupt is generated to notify

the MCU of this event).

The number of extra cycles can be programmed through the MCU_CK_CONF configuration

or to switch on any auxiliary clock generator. The maximum transition time from READY to

STANDBY is then:

Equation 9

where fclk is the digital clock frequency (typically 26 MHz).

The transition to SLEEP state causes the MCU clock source to change from XO to RCO.

Similarly, when the STS1TX exits SLEEP to any active state, the source is the XO. Both

these transitions are implemented in order to be glitch-free. This is guaranteed by

synchronizing both transitions, switching on the rising or falling edge of the RCO clock.

The clock provided to the MCU depends on the current state:

Table 33. MCU clock vs. state

State Source oscillator MCU clock

SHUTDOWN N/A N/A

STANDBY N/A Tail

SLEEP RC Osc RC/1 or RC/128

READY

TUNING

XTAL XTAL/N

TREADY STANDBY

Δ1

fclk

--------512

1192⁄

-----------------98304

fclk

----------------=⋅=

DocID025109 Rev 1 55/70

STS1TX Register table

11 Register table

This section describes all the registers used to configure the STS1TX. The description is

structured in sections according to the register usage.

STS1TX has three types of registers:

•Read and write (R/W), which can be completely managed by SPI using READ and

WRITE operations

•Read-only (R)

•Read-and-reset (RR), is automatically cleared after a READ operation.

A further category of special registers collects the ones which cannot be categorized in any

of the three mentioned above R/W, R, or RR.

The fields named as “Reserved” must not be overridden by the user. Otherwise, behavior is

not guaranteed.

The memory map is shown in the following table:

Table 34. General configuration registers

ANA_FUNC_CONF[1] 0x00

7:5 Reserved 000

R/W

4:2 GM_CONF[2:0] 011 Sets the driver gm of the XO at

startup

1:0 SET_BLD_LVL[1:0] 00

Sets the BLD threshold

00: 2.7 V

01: 2.5 V

10: 2.3 V

11: 2.1 V

56/70 DocID025109 Rev 1

ANA_FUNC_CONF[0] 0x01

7Reserved 1

R/W

6 24_26MHz_SELECT 1

1: 26 MHz configuration

0: 24 MHz configuration

(impact only RCO calibration

reference and loop filter

tuning)

5 AES_ON 0 1: AES engine enabled

4 EXT_REF 0

0: reference signal from XO

circuit

1: reference signal from XIN

3Reserved 0

2BROWN_OUT 0 1: enables accurate brownout

detection

1 BATTERY_LEVEL 0 1: enables battery level

detector circuit

0TS 01: enables the “temperature

sensor” function

GPIO3_CONF 0x02

7:3 GPIO_SELECT[4:0] 10100

R/W

GPIO3 configuration (default:

digital GND)

2Reserved 0

1:0 GPIO_MODE[1:0] 10

GPIO3 mode:

01b: digital input

10b: digital output low power

11b: digital output high power

(default: digital output low

power)

GPIO2_CONF 0x03

7:3 GPIO_SELECT[4:0] 10100

R/W

GPIO2 configuration (default:

digital GND)

2Reserved 0

1:0 GPIO_MODE 10

GPIO2 mode:

01b: digital input

10b: digital output low power

11b: digital output high power

(default: digital output low

power)

Table 34. General configuration registers (continued)

DocID025109 Rev 1 57/70

STS1TX Register table

GPIO1_CONF 0x04

7:3 GPIO_SELECT[4:0] 10100

R/W

GPIO1 configuration (default:

digital GND)

2Reserved 0

1:0 GPIO_MODE 10

GPIO1 mode:

01b: digital input

10b: digital output low power

11b: digital output high power

(default: digital output low

power)

GPIO0_CONF 0x05

7:3 GPIO_SELECT[4:0] 00001

R/W

GPIO0 configuration (default:

power-on reset signal)

2Reserved 0

1:0 GPIO_MODE 10

GPIO0 mode:

00b: analog

01b: digital input

10b: digital output low power

11b: digital output high power

(default: digital output low

power)

MCU_CK_CONF 0x06

7 EN_MCU_CLK 0

R/W

1: The internal divider logic is

running, so the MCU clock is

available (but proper GPIO

configuration is needed)

6:5 CLOCK_TAIL[1:0] 0

Number of extra clock cycles

provided to the MCU before

switching to STANDBY state:

00: 0 extra clock cycle

01: 64 extra clock cycles

10: 256 extra clock cycles

11: 512 extra clock cycles

4:1 XO_RATIO[3:0] 0 Divider for the XO clock output

0 RCO_RATIO 0

Divider for the RCO clock

output

0: 1

1: 1/128

XO_RCO_TEST 0xB4

7:4 Reserved 0010

3 PD_CLKDIV 0

1: disable both dividers of the

digital clock (and reference

clock for the SMPS) and IF-

ADC clock.

2:0 Reserved 001

Table 34. General configuration registers (continued)

58/70 DocID025109 Rev 1

SYNTH_CONFIG[0] 0x9F

7 SEL_TSPLIT 0

R/W

0: split time: 1.75 ns

1: split time: 3.47 ns

6:0 Reserved 0100000

SYNTH_CONFIG[1] 0x9E

7REFDIV 0

R/W

Enable division by 2 on the

reference clock:

0: fREF = fXO frequency

1: fREF = fXO frequency / 2

6:3 Reserved 1011

2 VCO_L_SEL 0 1: enable VCO_L

1 VCO_H_SEL 1 1: enable VCO_H

0Reserved 1

Table 34. General configuration registers (continued)

Table 35. Radio configuration registers (analog blocks)

SYNT3 0x08

7:5 WCP[2:0] 000

R/W

Set the charge pump current

according to the VCO

frequency. See Ta ble 24.

4:0 SYNT[25:21] 01100

SYNT[25:21], highest 5 bits of

the PLL programmable divider

The valid range depends on

fXO and REFDIV settings; for

fXO=26MHz. See Equation 2

SYNT2 0x09 7:0 SYNT[20:13] 0x84 R/W

SYNT[20:13], intermediate bits

of the PLL programmable

divider. See Equation 2

SYNT1 0x0A 7:0 SYNT[12:5] 0xEC R/W

SYNT[12:5], intermediate bits

of the PLL programmable

divider. See Equation 2

SYNT0 0x0B

7:3 SYNT[4:0] 01010 R/W

SYNT[4:0], lowest bits of the

PLL programmable divider.

See Equation 2

2:0 BS 001 R/W

Synthesizer band select. This

parameter selects the out-of-

loop divide factor of the

synthesizer (B in Equation 2).

1: 6 Band select factor for high

band

3: 12 Band select factor for

middle band

4: 16 Band select factor for low

band

5: 32 Band select factor for

very low band

DocID025109 Rev 1 59/70

STS1TX Register table

CHSPACE 0x0C 7:0 CH_SPACING 0xFC R/W

Channel spacing in steps of

fXO/215 (~793 for fXO = 26 MHz,

~732 for fXO = 24 MHz).

FC_OFFSET[1] 0x0E

7:4 Reserved 0

R/W

Carrier offset in steps of fXO/218

and represented as 12 bits 2-

complement integer. It is added

/ subtracted to the carrier

frequency set by the SYNTx

used to set a fixed correction

value obtained e.g. from crystal

measurements.

3:0 FC_OFFSET[11:8] 0

FC_OFFSET[0] 0x0F 7:0 FC_OFFSET[7:0] 0 R/W

PA_POWER[8] 0x10

7Reserved 0

R/W Output power level for 8th slot

(+12 dBm)

6:0 PA_LEVEL_7 000001

PA_POWER[7] 0x11

7Reserved 0

R/W Output power level for 7th slot

(+6 dBm)

6:0 PA_LEVEL_6 000111

PA_POWER[6] 0x12

7Reserved 0

R/W Output power level for 6th slot

(0 dBm)

6:0 PA_LEVEL_5 001101

PA_POWER[5] 0x13

7Reserved 0

R/W Output power level for 5th slot (-

6 dBm)

6:0 PA_LEVEL_4 010010

PA_POWER[4] 0x14

7Reserved 0

R/W Output power level for 4th slot (-

12 dBm)

6:0 PA_LEVEL_3 011010

PA_POWER[3] 0x15

7Reserved 0

R/W Output power level for 3rd slot

(-18 dBm)

6:0 PA_LEVEL_2 100000

PA_POWER[2] 0x16

7Reserved 0

R/W Output power level for 2nd slot

(-24 dBm)

6:0 PA_LEVEL_1 100111

PA_POWER[1] 0x17

7Reserved 0

R/W Output power level for first slot

(-30 dBm)

6:0 PA_LEVEL_0 000000

Table 35. Radio configuration registers (analog blocks) (continued)

60/70 DocID025109 Rev 1

PA_POWER[0] 0x18 7:6 CWC[1:0] 00

R/W

Output stage additional load

capacitors bank (to be used to

optimize the PA for different

sub-bands):

00: 0 pF

01: 1.2 pF

10: 2.4 pF

11: 3.6 pF

5 PA_RAMP_ENABLE 0 1: enable the power ramping

4:3 PA_RAMP_STEP_W

IDTH[1:0] 00 Step width (unit: 1/8 of bit

period)

2:0 PA_LEVEL_MAX_IN

DEX 111 Final level for power ramping or

selected output power index.

Table 35. Radio configuration registers (analog blocks) (continued)

Table 36. Radio configuration registers (digital blocks)

MOD1 0x1A 7:0 DATARATE_M 0x83 R/W The mantissa value of the data

rate equation (see Equation 8)

MOD0 0x1B

7CW 0

R/W

1: enable the CW transmit

mode

6 BT_SEL 0

Select BT value for GFSK

0: BT = 1

1: BT = 0.5

5:4 MOD_TYPE[1:0] 01

Modulation type

0: 2-FSK

1: GFSK

2: ASK/OOK

3: MSK

3:0 DATARATE_E 1010 The exponent value of the data

rate equation (see Equation 8)

FDEV0 0x1C

7:4 FDEV_E[3:0] 0100

R/W

The exponent value of the

frequency deviation equation

(see Equation 7)

3CLOCK_REC_ALGO

_SEL 0Select PLL or DLL mode for

symbol timing recovery

2:0 FDEV_M 101

The mantissa value of the

frequency deviation equation

(see Equation 7)

DocID025109 Rev 1 61/70

STS1TX Register table

Table 37. Packet/protocol configuration registers

PCKTCTRL4 0x30

7:5 Reserved 000

R/W

4:3 ADDRESS_LEN[1:0] 00

Length of address field in

bytes:

0 or 1: Basic

2: STack

2:0 CONTROL_LEN 000 Length of control field in

bytes

PCKTCTRL3 0x31

7:6 PCKT_FRMT[1:0] 00

R/W

Format of packet.

0: basic,

2: WM-Bus,

3: STack

(see Section 9.5)

5:4 Reserved 00

3:0 LEN_WID 0111 Size in number of binary digit

of length field

PCKTCTRL2 0x32

7:3 PREAMBLE_LENGTH[

4:0] 00011

R/W

Length of preamble field in

bytes (from 1 to 32)

2:1 SYNC_LENGTH[1:0] 11 Length of sync field in bytes

(from 1 to 4)

0 FIX_VAR_LEN 0

Packet length mode.

0: fixed,

1: variable (in variable mode

the field LEN_WID of

PCKTCTRL3 register must

be configured)

PCKTCTRL1 0x33

7:5 CRC_MODE[2:0] 001

R/W

CRC:

0: No CRC,

1: 0x07,

2: 0x8005,

3: 0x1021,

4: 0x864CBF

4WHIT_EN[0] 0

1: enable the whitening mode

on the data

(see Section 9.4.3)

3:2 TXSOURCE[1:0] 00

TX source data:

0: normal mode,

1: direct through FIFO,

2: direct through GPIO,

3: PN9

1Reserved 0

0FEC_EN 0 1: enable the FEC encoding

in TX. (see Section 9.4.1)

62/70 DocID025109 Rev 1

PCKTLEN1 0x34 7:0 PCKTLEN1 0 R/W Length of packet in bytes

(MSB)

PCKTLEN0 0x35 7:0 PCKTLEN0 0x14 R/W Length of packet in bytes

(LSB)

SYNC4 0x36 7:0 SYNC4 0x88 R/W Sync word 4

SYNC3 0x37 7:0 SYNC3 0x88 R/W Sync word 3

SYNC2 0x38 7:0 SYNC2 0x88 R/W Sync word 2

SYNC1 0x39 7:0 SYNC1 0x88 R/W Sync word 1

MBUS_PRMBL 0x3B 7:0 MBUS_PRMBL[7:0] 0x20 R/W MBUS preamble length in

chip sequence ‘01’

MBUS_PSTMBL 0x3C 7:0 MBUS_PSTMBL[7:0] 0x20 R/W MBUS postamble length in

chip sequence ‘01’

MBUS_CTRL 0x3D

7:4 Reserved 00000

R/W3:1 MBUS_SUBMODE[2:0

]000

MBUS sub mode: allowed

values are 0, 1, 3 and 5

WM-BUS sub mode:

0: S1 S2 long header,

1: S1m S2 T2 other to meter,

3: T1 T2 meter to other,

5: R2 short header

0Reserved 0

FIFO_CONFIG[1] 0x40

7 Reserved 0 R/W

6:0 TXAFTHR [6:0] 110000 R/W FIFO almost full threshold for

TX FIFO

FIFO_CONFIG[0] 0x41

7 Reserved 0 R/W

6:0 TXAETHR [6:0] 110000 R/W FIFO almost empty threshold

for TX FIFO

PCKT_FLT_GOALS[3] 0x4B 7:0 TX_DEST_ADDR 0 R/W TX packet destination fields

PCKT_FLT_GOALS[0] 0x4E 7:0 TX_SOURCE_ADDR 0 R/W TX packet source

PROTOCOL[2] 0x50

23:2

1Reserved 0

R/W

1: CS value contributes to

timeout disabling

20:1

TX_SEQ_NUM_RELO

AD[1:0] 0

TX sequence number to be

used when counting reset is

required using the related

command.

18 RCO_CALIBRATION 0 1: enable the automatic RCO

calibration

17 VCO_CALIBRATION 1 1: enable the automatic VCO

calibration

16 LDC_MODE 0 1: LDC mode on

Table 37. Packet/protocol configuration registers (continued)

DocID025109 Rev 1 63/70

STS1TX Register table

PROTOCOL[1] 0x51

15:1

2Reserved 0000

R/W

11 SEED_RELOAD 0

1: reload the back-off random

generator seed using the

value written in the

BU_COUNTER_SEED_MSB

YTE / LSBYTE registers

10 CSMA_ON 0 1: CSMA channel access

mode enabled

9 CSMA_PERS_ON 0 1: CSMA persistent (no back-

off) enabled

8Reserved 0

PROTOCOL[0] 0x52

7:4 Reserved 0

R/W3NACK_TX 1 1: field NO_ACK=1 on

transmitted packet

2:0 Reserved 0

TIMERS[3] 0x55 31:2

LDC_PRESCALER[7:0

]1R/W

Prescaler value of the LDC

wakeup timer. When this

timer expires the STS1TX

exits SLEEP state.

TIMERS[2] 0x56 23:1

6LDC_COUNTER[7:0] 0 R/W

Counter value of the LDC

wakeup timer. When this

timer expires the STS1TX

exits SLEEP state.

TX_CTRL_FIELD[3] 0x68 7:0 TX_CTRL3 0 R/W Control field value to be used

in TX packet as byte n.3

TX_CTRL_FIELD[2] 0x69 7:0 TX_CTRL2 0 R/W Control field value to be used

in TX packet as byte n.2

TX_CTRL_FIELD[1] 0x6A 7:0 TX_CTRL1 0 R/W Control field value to be used

in TX packet as byte n.1

TX_CTRL_FIELD[0] 0x6B 7:0 TX_CTRL0 0 R/W Control field value to be used

in TX packet as byte n.0

PM_CONFIG[2] 0xA4

7Reserved 0

R/W

6 EN_TS_BUFFER 0 1: temperature sensor output

is buffered

5 DISABLE_SMPS 0 0: enable internal SMPS

1: disable internal SMPS

4Reserved 0

3 SET_SMPS_VTUNE 1 Sets the SMPS Vtune voltage

2 SET_SMPS_PLLBW 1 Sets the SMPS bandwidth

1:0 Reserved 00

Table 37. Packet/protocol configuration registers (continued)

64/70 DocID025109 Rev 1

PM_CONFIG[1] 0xA5

7 EN_RM 0

R/W

0: divider by 4 enabled

(SMPS' switching frequency

is FSW=FOSC/4)

1: rate multiplier enabled

(SMPS' switching frequency

is FSW=KRM*FOSC/(2^15)

6:0 KRM[14:8] 0100000 Sets the divider ration of the

rate multiplier.

PM_CONFIG[0] 0xA6 7:0 KRM[7:0] 0 R/W

XO_RCO_CONFIG 0xA7

7:4 Reserved 1110

R/W3 EXT_RCOSC 0 1:the 34.7kHz signal must be

supplied from a GPIO pin

2:0 Reserved 001

TEST_SELECT 0xA8 7:0 Reserved 0x00

R/W

PM_TEST 0xB2 7:0 Reserved 0x42

Table 37. Packet/protocol configuration registers (continued)

Table 38. Frequently used registers

CHNUM 0x6C 7:0 CH_NUM 0 R/W

Channel number. This value is

multiplied by the channel

spacing and added to the

synthesizer base frequency to

generate the actual RF carrier

frequency. See Equation 2

VCO_CONFIG 0xA1

7:6 Reserved 00

R/W

5:0 VCO_GEN_CURR 010001 Set the VCO current

RCO_VCO_CALIBR_IN

[2] 0x6D

7:4 RWT_IN[3:0] 0111

R/W

RWT word value for the RCO

3:0 RFB_IN[4:1] 0000

RFB word value for the RCO

RCO_VCO_CALIBR_IN

[1] 0x6E

7 RFB_IN[0] 0

R/W

6:0 VCO_CALIBR_TX[6:

100100

Word value for the VCO to be

used in TX mode

AES_KEY_IN[15] 0x70 7:0 AES_KEY15 0 R/W AES engine key input (128

bits)

AES_KEY_IN[14] 0x71 7:0 AES_ KEY14 0 R/W AES engine key input (128

bits)

…7:0 … ………

AES_KEY_IN[1] 0x7E 7:0 AES_ KEY1 0 R/W AES engine key input (128

bits)

AES_KEY_IN[0] 0x7F 7:0 AES_ KEY0 0 R/W AES engine key input (128

bits)

DocID025109 Rev 1 65/70

STS1TX Register table

AES_DATA_IN[15] 0x80 7:0 AES_IN15 0 R/W AES engine data input (128

bits)

AES_DATA_IN[14]

0x81 7:0 AES_IN14 0 R/W AES engine data input (128

bits)

…… … ………

AES_DATA_IN[1] 0x8E 7:0 AES_IN1 0 R/W AES engine data input (128

bits)

AES_DATA_IN[0] 0x8F 7:0 AES_IN0 0 R/W AES engine data input (128

bits)

IRQ_MASK[3] 0x90 7:0 INT_MASKT[31:24] 0 R/W

The IRQ mask register to route

the IRQ information to a GPIO.

See Table 29.

IRQ_MASK[2] 0x91 7:0 INT_MASK [23:16] 0 R/W

The IRQ mask register to route

the IRQ information to a GPIO.

See Table 29.

IRQ_MASK[1] 0x92 7:0 INT_MASK[15:8] 0 R/W

The IRQ mask register to route

the IRQ information to a GPIO.

See Table 29.

IRQ_MASK[0] 0x93 7:0 INT_MASK [7:0] 0 R/W

The IRQ mask register to route

the IRQ information to a GPIO.

See Table 29.

DEM_CONFIG 0xA3

7:2 Reserved 001101

R/W

Reserved do not modify

1 DEM_ORDER 1 Set it to 0 during radio

initialization

0 Reserved 1 Reserved do not modify

PM_CONFIG 0xA4

7 Reserved 0

R/W

6EN_TS_BUFFER 0 1: temperature sensor output

is buffered

5 DISABLE_SMPS 0 0: enable internal SMPS

1: disable internal SMPS

MC_STATE[1] 0xC0

7:3 Reserved 0101

2 TX_FIFO_FULL 0 1: TX FIFO is full

1 Reserved 0

0 ERROR_LOCK 0 1: RCO calibrator error

MC_STATE[0] 0xC1

7:1 STATE[6:0] 0

Current MC state. See

Table 18.

0 XO_ON 0 1: XO is operating

TX_PCKT_INFO 0xC2

7:6 Reserved 0

R5:4 TX_SEQ_NUM 0 Current TX packet sequence

number

3:0 Reserved 0

Table 38. Frequently used registers (continued)

66/70 DocID025109 Rev 1

AES_ DATA_OUT[15] 0xD4 7:0 AES_OUT15 0 R AES engine data output (128

bits)

AES_ DATA_OUT[14]

0xD5 7:0 AES_OUT14 0 R AES engine data output (128

bits)

…… … ………

AES_ DATA_OUT[1] 0xE2 7:0 AES_OUT1 0 R AES engine data output (128

bits)

AES_ DATA_OUT[0] 0xE3 7:0 AES_OUT0 0 R AES engine data output (128

bits)

RCO_VCO_CALIBR_O

UT[1] 0xE4

7:4 RWT_OUT[3:0] 0

RWT word from internal RCO

calibrator

3:0 RFB_OUT[4:1] 0 RFB word from internal RCO

calibrator

RCO_VCO_CALIBR_O

UT[0] 0xE5

7RFB_OUT[0] 0

6:0 VCO_CALIBR_DATA 0 Output word from internal VCO

calibrator

LINEAR_FIFO_STATUS

[1] 0xE6

7 Reserved 0

6:0 ELEM_TXFIFO 0

Number of elements in the

linear TX FIFO (from 0 to 96

bytes)

IRQ_STATUS[3] 0xFA 7:0 INT_EVENT[31:24] 0 RR The IRQ status register. See

Table 29.

IRQ_STATUS[2] 0xFB 7:0 INT_EVENT[23:16] 0 RR The IRQ status register. See

Table 29.

IRQ_STATUS[1] 0xFC 7:0 INT_EVENT[15:8] 0 RR The IRQ status register. See

Table 29.

IRQ_STATUS[0] 0xFD 7:0 INT_EVENT[7:0] 0 RR The IRQ status register. See

Table 29.

Table 38. Frequently used registers (continued)

Table 39. General information

DEVICE_INFO[1:0]

0xF0 7:0 PARTNUM[7:0] 0x01 R Device part number

0xF1 7:0 VERSION[7:0] 0x30 R Device version number

DocID025109 Rev 1 67/70

STS1TX Package mechanical data

12 Package mechanical data

In order to meet environmental requirements, ST offers these devices in different grades of

ECOPACK® packages, depending on their level of environmental compliance. ECOPACK

specifications, grade definitions, and product status are available at: www.st.com.

ECOPACK is an ST trademark.

Table 40. QFN20 (4 x 4 mm.) mechanical data

Dim. mm.

Min. Typ. Max.

A 0.80 0.90 1.00

A1 0.02 0.05

A2 0.65 1.00

A3 0.25

b 0.18 0.23 0.30

D 3.85 4.00 4.15

D2 2.55 2.60 2.65

E 3.85 4.00 4.15

E2 2.55 2.60 2.65

e 0.45 0.50 0.55

L 0.35 0.55 0.75

ddd 0.08

SEAT1NG PLANE C "7 <( 15="" em="" qddd="" c="" a1="" e2="" juvul="" d="" 4‘="" e="" $="" pin="" #1="" r2020="" 16="" 20="" u="" u="" u="" 1="" 6’="" w="" +="" m="" 1m="" 11="" m="" 1o="" d2="" 13$="" bottom="" view="" a2="" ._a-="" 1="" d="">

Package mechanical data STS1TX

68/70 DocID025109 Rev 1

Figure 13. QFN20 (4 x 4 mm.) drawing dimension

7169619_G

DocID025109 Rev 1 69/70

STS1TX Revision history

13 Revision history

Table 41. Document revision history

Date Revision Changes

07-Aug-2013 1 Initial release.

STS1TX

70/70 DocID025109 Rev 1

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