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ST25TA64K

RF command sets

42

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.

Note:

After receiving the deselect command, the session is released and ST25TA64K enters the

Standby power mode.

In response to a RATS command, ST25TA64K returns FWI parameter (default frame waiting

time used); when ST25TA64K needs more time for a command execution, it requests a

frame waiting time extension by responding 0xF2 0xWTX (Request waiting time = FWI *

WTX). If the reader accepts ST25TA64K request, it acknowledges by sending the command

0xF2 0xWTX. The frame waiting time becomes FWI * WTX for the current command only.

Table 15. S-Block format

NFC frame

SoD

EoD

PCB

DID

Payload

CRC

Length

1 byte

1 byte

1 to 255 bytes

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)

2 CRC bytes

1. This field is present when b5-b4 bits are set to 0b11 (S-Block is a WTX). see Table 16: S-Block detailed format.

Table 16. S-Block detailed format

b7-b6

b5-b4

b3

b2

b1

b0

0b11

X

X

0

1

0

S-Block

0b00: Deselect

0b11: WTX

0: DID field is not present

1: DID field is present

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RFU

RFU