RESET

RTS

UART RX

SLEEP

UART TX

SUSPEND

Vcc

X201

X200

L202

X202

X203

Vcc

Vcc

Vcc

Vcc

Vcc

X207

X208

L204

1

2

X1

Host MCU

Host MCU

Asynchronous Mode

L203

Antenna

1

2

3

4

5

6

7

8

9

10

21

22

23

24

25

26

27

28

29

30

GND

GND

GND

GND

BR3/FAST SPI

DVDD2

BR2/SCLK

TxD/SOUT

BR1/SFLOW

RxD/SIN

AVDD4

AVDD1

R_BIAS

AVDD5

XOSC_Q1

RF_N

RF_P

AVDD3

XOSC_Q2

AVDD2

C200

C208

C209

C211

C207

C206

C202

C205

C204

Set

Baud

Rate

C210

C203

R200

C201

U200

CC257X

X3

S0505-01

CC2570

CC2571

www.ti.com

SWRS095A

– FEBRUARY 2011 – REVISED MARCH 2011

The asynchronous serial interface may be used with a UART peripheral on an external MCU. The baud rates are

selectable via a hardware pin configuration.

Byte-synchronous serial may be used with an SPI peripheral (three-wire), though flow control must be

implemented in software using GPIOs. The bit-synchronous serial interface is designed to be implemented in

software on the external MCU, allowing the interface to be implemented using GPIOs only.

ASYNCHRONOUS SERIAL INTERFACE

The asynchronous serial interface is selected by setting the PORTSEL pin to VSS (GND). The asynchronous

serial interface is functionally equivalent to a standard UART with 8 data bits, no parity, and 1 stop bit. Unlike a

standard UART, the asynchronous serial interface supports unidirectional flow control only. Using the

asynchronous serial interface also requires that the host MCU tightly control the SLEEP state of the CC257x by

using the SLEEP and SUSPEND control lines. The following block diagram shows the interconnections required

for the asynchronous serial interface.

Figure 8. Asynchronous Serial Hardware Setup

The baud rate is selected using a hardware pin configuration using pins BR1, BR2, and BR3. Table 2 lists the

available baud rates and the corresponding pin configurations.

Copyright

© 2011, Texas Instruments Incorporated

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