CRX14_05 Datasheet, PDF(14/40 Page) STMicroelectronics – Low Cost ISO14443 type-B Contactless Coupler Chip with Anti-Collision, CRC Management and Anti-Clone Function

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CRX14_05 Datasheet, PDF (14/40 Pages) STMicroelectronics – Low Cost ISO14443 type-B Contactless Coupler Chip with Anti-Collision, CRC Management and Anti-Clone Function

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CRX14

The STOP condition at the end of a Write access

to the Input/Output Frame, Authenticate or Anti-

Collision Register, causes the Radio Frequency

data exchange between the CRX14 and the PICC

to be started.

During the Radio Frequency data exchange, the

CRX14 disconnects itself from the IÂ²C bus. The

time (tRFEX) needed to complete the exchange is

not fixed as it depends on the PICC command for-

mat. To know when the exchange is complete, the

bus master uses an ACK polling sequence as

shown in Figure 9. It consists of the following:

Figure 8. CRX14 IÂ²C Write Mode Sequence

â Initial condition: a Radio Frequency data

exchange is in progress.

â Step 1: the master issues a START condition

followed by the first Byte of the new instruction

(Device Select Code plus R/W bit).

â Step 2: if the CRX14 is busy, no ACK is

returned and the master goes back to Step 1.

If the CRX14 has completed the Radio

Frequency data exchange, it responds with an

ACK, indicating that it is ready to receive the

second part of the next instruction (the first

Byte of this instruction being sent during Step

1).

BUS Master

CRX14 WRITE

BUS Slave

R/W

DEV SEL BYTE ADDR

DATA 1

DATA 2

DATA 3

ACK

DATA N

ACK

AI09265

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