CR14_10 STMICROELECTRONICS [STMicroelectronics], CR14_10 Datasheet - Page 31

• Manufacturer Part Number: CR14_10
• Description: ISO14443 type-B contactless coupler chip with anti-collision and CRC management
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

CR14
7
7.1
Figure 28. Standard TAG command: request frame transmission
I²C
RF
S
T
A
R
T
Device
Select
Code
Register
Address
Output
Input/
01h
Tag access using the CR14 coupler
In all the following I²C commands, the last three bits of the Device Select Code can be
replaced by any of the three-bit binary values (000, 001, 010, 011, 100, 101, 110, 111).
These values are linked to the logic levels applied to the E2, E1 and E0 pads of the CR14.
Standard TAG command access description
Standard PICC commands, like Read and Write, are generated by the CR14 using the
Input/Output Frame Register.
When the host needs to send a standard frame command to the PICC, it first has to
internally generate the complete frame, with the command code followed by the command
parameters. Only the two CRC Bytes should not be generated, as the CR14 automatically
adds them during the RF transmission.
When the frame is ready, the host has to write the request frame into the Input/Output Frame
Register using the I²C write command specified in
condition, the CR14 inserts the I²C Bytes in the required ISO character format (
and starts to transmit the request frame to the PICC. Once the RF transmission is over, the
CR14 waits for the PICC to send an answer frame.
If the PICC answers, the characters received
stored into the Input/Output Frame Register, as specified in
transmission, the CR14 disconnects itself from the I²C bus. On reception of the PICC EOF,
the CR14 checks the CRC and reconnects itself to the I²C bus.
The host can then get the PICC answer frame by issuing an Input/Output Frame Register
Read on the I²C bus, as specified in Figures
If no answer from the PICC is detected after a time-out delay, fixed in the Parameter
Register (bits b
Request
Length
Frame
N
Code
Data 1
TAG
Cmd
Param
5
Data 2
and b
Param
Data
6
), the Input/Output Frame Register is set as specified in
Param
Data N
Doc ID 11922 Rev 2
S
T
O
P
CR14
SOF
SOF
Data 1
14
TAG
Cmd
Code
(Figure
and 15.
Figure 13 on page
Data 2
Param
26) are demodulated, decoded and
Tag access using the CR14 coupler
Param
Data
Table
Data N
Param
4. During the entire RF
23. After the I²C STOP
CRC
CRC
CRC
CRC
Table
Figure
SR14
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