ST25TA02K datasheet(24/50 Pages) STMICROELECTRONICS

24 / 50 page

RF command sets

ST25TA02K

24/50

DocID027801 Rev 1

5.4

S-Block format

The S-Block is used to exchange control information between a reader and a contactless

tag.

There are two requests using the S-Block format:

•

S(DES): the deselect command

•

S(WTX): the Waiting Frame eXtension command or response.

A Waiting Time eXtension request occurs in RF when the operating time needed by

ST25TA02K is greater than 19.2 ms.

The WTX field indicates the increase time factor to be used in this command execution

(FDTtemp = WTX * 19.2 ms). WTX depends on FWI.

Table 17. S-Block format

NFC frame

SoD

EoD

PCB

DID

Payload

CRC

Length

1 byte

2 bytes

0xC2: for S(DES) when the DID field is not present

0xCA: for S(DES) when the DID field is present

0xF2: for S(WTX) when the DID field is not present

0xFA: for S(WTX) when the DID field is present

DID field (optional)

WTX field (optional)(1)

1. This field is present when b5-b4 bits are set to 0b11 (S-Block is a WTX). see Table 18: S-Block detailed

format.

2 CRC bytes

Table 18. S-Block detailed format

b7-b6

b5-b4

0b11

S-Block

0b00: Deselect

0b11: WTX

0: DID field is not present

1: DID field is present

Must be set to 0

Must be set to 1

Must be set to 0

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