CR14 STMicroelectronics, CR14 Datasheet - Page 23

• Manufacturer Part Number: CR14
• Description: Low Cost Iso14443 Type-b Contactless Coupler Chip With Anti-collision And Crc Management
• Manufacturer: STMicroelectronics

CR14
5.2
Figure 13. Host-to-CR14 Transfer: I²C Write to Input/Output Frame Register for ISO14443B
Figure 14. CR14-to-Host Transfer: I²C Random Address Read from Input/Output Frame
Master
CR14
Bus
Master
CR14
Read
Bus
Slave
Write
Slave
Bus
Bus
S
T
A
R
T
S
T
A
R
T
1 0 1 0 XX X
I²C Input/Output Frame Register Protocol
Figure 13
Frame Register.
After the I²C STOP condition, the request frame is RF transmitted in the ISO14443 type-B
format. The CR14 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
The two CRC Bytes generated by the PICC are not stored.
The CR14 continues to output data Bytes until a NoACK has been generated by the I²C Host,
and received by the CR14. After all 36 Bytes have been output, the CR14 “rolls over”, and
starts outputting from the start of the Input/Output Frame Register again.
The CR14 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.
1 0 1 0XXX
Device
Select
Code
Register for ISO14443B
Device
Select
Code
R/W
R/W
ACK
shows how to store a PICC request frame command of N Bytes into the Input/Output
shows how to read an N-Byte PICC answer frame.
ACK
Input/Output
Register
Address
Input/Output
Register
Address
01h
01h
ACK
R
E
S
T
A
R
T
ACK
1 0 1 0 XXX
Request Frame
Device
Select
Code
Length N
N
R/W
ACK
ACK
Received
Length
Frame
N
Command
PICC
Code
Data 1
ACK
Answer
Data1
Frame
ACK
Data
5 Applying the I²C protocol to the CR14 registers
Command
Parameter
ACK
Data 2
PICC
Answer
Frame
Data 2
Data
ACK
ACK
Command
Parameter
PICC
Answer
Frame
Data
ACK
ACK
Command
Parameter
Data N
PICC
Data N
Answer
Frame
Data
NoACK
ai12041
ai12042
ACK
23/46
S
T
O
P
S
T
O
P