STRFNFCA datasheet(11/74 Pages) STMICROELECTRONICS

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STRFNFCA

Communication protocols

Doc ID 023077 Rev 10

11/74

Communication protocols

4.1

Universal asynchronous receiver/transmitter (UART)

The host sends commands to the STRFNFCA and waits for replies. Polling for readiness is

not necessary. The default baud rate is 57600 baud. The maximum allowed baud rate is

2 Mbps.

When sending commands, no data must be sent if the LEN field is zero.

When receiving data from the STRFNFCA, no data will be received if the LEN field is zero.

The formats of send and receive packets are identical.

If an ECHO command is sent, only one byte (0x55) is sent by the host.

Figure 7 shows an example of an ECHO command.

Caution:

UART communication is LSB first. Stop bit duration is two Elementary Time Units

(ETUs).

Note:

When STRFNFCA leaves WFE mode (from Power-up, Hibernate, Sleep/Field Detector or

Tag Detector) following an |RQ_IN/RX low level pulse, this pulse is NOT interpreted as the

UART start bit character.

If the user loses UART synchronization, it can be recovered by sending an ECHO command

until a valid ECHO reply is received. Otherwise, after a maximum of 255 ECHO commands,

Figure 6.

UART communication

Figure 7.

ECHO command and response example

Sending commands to the STRFNFCA

Receiving data from the STRFNFCA

CMD

LEN

DATA

Several data bytes

Resp Code

LEN

DATA

Several data bytes

Ai18122

Int.

Clock

012

4567

10101010

(Stop)

(Echo 0x55)

Host to STRFNFCA

STRFNFCA to Host

(Start)

10101010

(Stop)

(Echo 0x55)

(Start)

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