CR14 STMicroelectronics, CR14 Datasheet - Page 31

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

CR14
7
7.1
Figure 28. Standard TAG Command: Request Frame Transmission
I²C
RF
S
T
A
R
T
Device
Select
Code
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 (
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
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
Register
Address
Output
Input/
01h
5
Request
Length
Frame
and b
N
Code
Data 1
6
TAG
Cmd
), the Input/Output Frame Register is set as specified in
Param
Data 2
Param
Data
Param
Data N
S
T
O
P
14
CR14
SOF
SOF
and 15.
(Figure
Data 1
TAG
Cmd
Code
Figure 13 on page
26) are demodulated, decoded and stored
Table
Data 2
Param
4. During the entire RF
Param
Data
7 Tag access using the CR14 coupler
Data N
Param
23. After the I²C STOP
Table
CRC
CRC
4.
Figure
CRC
CRC
20) and
SR14
EOF
EOF
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