CRX14_05 Datasheet, PDF (18/40 Pages) STMicroelectronics – Low Cost ISO14443 type-B Contactless Coupler Chip with Anti-Collision, CRC Management and Anti-Clone Function

CRX14
I²C Input/Output Frame Register Protocol
Figure 14. 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 15. shows how to read an N-Byte PICC an-
swer 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 Ad-
dress Read mode can be used if the previous
command was issued to the register where the
Read is to take place.
Figure 14. Host-to-CRX14 Transfer: I²C Write to Input/Output 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
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Figure 15. CRX14-to-Host Transfer: I²C Random Address Read
from Input/Output 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
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Figure 16. CRX14-to-Host Transfer: I²C Current Address Read
from I/O Frame Register for ISO14443B
Bus Master
S
T
A
R
T
Device
Select
Code
R/W
ACK
ACK
ACK
ACK
NoACK
S
T
O
P
CRX14 Write
Bus Slave
1 0 1 0 XX X
N
Data 1
Data 2
Data N
Received Answer Frame Answer Frame Answer Frame Answer Frame
Frame Length
ACK
Data
Data
Data
Data
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