CRX14_10 Datasheet, PDF (23/47 Pages) STMicroelectronics – ISO14443 type-B contactless coupler chip with anti-collision, CRC management and anti-clone function

CRX14
Applying the I²C protocol to the CRX14 registers
5.2
I²C input/output frame register protocol
Figure 13 shows how to store a PICC request frame command of N Bytes into the
Input/Output Frame Register.
After the I²C STOP condition, the request frame is RF transmitted in the ISO14443 type-B
format. The CRX14 then waits for the PICC answer frame which will also be stored in the
Input/Output Frame Register. The request frame is over-written by the answer frame.
Figure 14 shows how to read an N-Byte PICC answer frame.
The two CRC Bytes generated by the PICC are not stored.
The CRX14 continues to output data Bytes until a NoACK has been generated by the I²C
Host, and received by the CRX14. After all 36 Bytes have been output, the CRX14 “rolls
over”, and starts outputting from the start of the Input/Output Frame Register again.
The CRX14 supports the I²C Current Address and Random Address Read modes. The
Current Address Read mode can be used if the previous command was issued to the
register where the Read is to take place.
Figure 13. Host-to-CRX14 transfer: I²C write to I/O frame register for ISO14443B
S
Bus
Master
T
A
R
T
Device
Select
Code
R/W
Input/Output
Register
Address
CRX14
Write ^{1 0 1 0 XX X}
01h
Request Frame
Length N
N
PICC
Command
Code
Data 1
PICC
Command
Parameter
Data 2
PICC
Command
Parameter
PICC
S
Command ^T
Parameter ^O
P
Data N
Bus
Slave
ACK
ACK
ACK
ACK
ACK
ACK
ACK
ai09243
Figure 14. CRX14-to-host transfer: I²C random address read from I/O frame register for
ISO14443B
S
T
Bus A
Master ^R
T
R/W
Device Input/Output
Select
Register
Code
Address
CRX14
Read ^{1 0 1 0XXX}
01h
R
E
S
R/W
T ^Device
A Select
R
T
Code
10 1 0XXX
ACK
ACK
ACK
N
Data1
Data 2
ACK
NoACK
S
T
O
P
Data N
Bus
Slave
ACK
ACK
Received
ACK ^Frame
Length
Answer
Frame
Data
Answer
Frame
Data
Answer
Frame
Data
Answer
Frame
Data
ai09243
Doc ID 8880 Rev 4
23/47