CR14 datasheet(24/46 Pages) STMICROELECTRONICS

24 / 46 page

5 Applying the I²C protocol to the CR14 registers

CR14

24/46

Figure 15. CR14-to-Host Transfer: I²C Current Address Read from I/O Frame Register

for ISO14443B

5.3

I²C Slot Marker Register Protocol

An I²C Write command to the Slot Marker Register generates an automated sixteen-command

loop (See Figure 16 for a description of the command).

All the answers from the ST short range memory devices that are detected, are written in the

Input/Output Frame Register.

Read from the I²C Slot Marker Register is not supported by the CR14. If the I²C Host tries to

read the Slot Marker Register, the CR14 will return the data value FFh in both Random Address

and Current Address Read modes until NoACK is generated by the I²C Host.

The result of the detection sequence is stored in the Input/Output Frame Register. This

Figure 16. Host-to-CR14 Transfer: I²C Write to Slot Marker Register

10 1 0 XX X

ACK

Answer Frame

Data

Device

Select

Code

Bus Master

CR14 Write

Bus Slave

ai12043

R/W

Data 1

Data 2

Answer Frame

Data

Answer Frame

Data

Data N

Answer Frame

Data

Received

Frame Length

ACK

NoACK

ACK

03h

ACK

Slot Marker

Address

Bus Master

CR14 Write

Bus Slave

ai12044

1010 X X X

Device Select

Code

R/W

ACK

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