CRX14_05 Datasheet, PDF (26/40 Pages) STMicroelectronics – Low Cost ISO14443 type-B Contactless Coupler Chip with Anti-Collision, CRC Management and Anti-Clone Function

CRX14
TAG ACCESS USING THE CRX14 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 CRX14.
Standard TAG Command Access Description
Standard PICC commands, like Read and Write,
are generated by the CRX14 using the Input/Out-
put Frame Register.
When the host needs to send a standard frame
command to the PICC, it first has to internally gen-
erate the complete frame, with the command code
followed by the command parameters. Only the
two CRC Bytes should not be generated, as the
CRX14 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 Regis-
ter using the I²C write command specified in Fig-
ure 14., page 18. After the I²C STOP condition, the
CRX14 inserts the I²C Bytes in the required ISO
character format ( Figure 21.) and starts to trans-
mit the request frame to the PICC. Once the RF
transmission is over, the CRX14 waits for the
PICC to send an answer frame.
If the PICC answers, the characters received ( Fig-
ure 27.) are demodulated, decoded and stored
into the Input/Output Frame Register, as specified
in Table 4. During the entire RF transmission, the
CRX14 disconnects itself from the I²C bus. On re-
ception of the PICC EOF, the CRX14 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 15 and 16.
If no answer from the PICC is detected after a
time-out delay, fixed in the Parameter Register
(bits b₅ and b₆), the Input/Output Frame Register
is set as specified in Table 4.
Figure 29. Standard TAG Command: Request Frame Transmission
S
T
A
R
T
Device
Select
Code
I²C
Input/
Output
Register
Address
Request
Frame
Length
01h
N
TAG
Cmd
Code
Param
Param
Data 1 Data 2 Data
S
Param
T
O
P
Data N
CRX14
SOF
TAG
Cmd
Code
Param
Param
Param
CRC
CRC
SRX14
EOF
RF
SOF
Data 1 Data 2
Data
Data N
CRC
CRC
EOF
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Figure 30. Standard TAG Command: Answer Frame Reception
TAG
SOF
I²C
TAG
Data
TAG
Data
TAG
Data
TAG
Data
TAG
CRC
TAG
CRC
TAG
EOF
S
T
A
R
T
Device
Select
Code
Input/
Output
Register
Address
01h
Answer
Frame
Length
P
TAG
Data
TAG
Data
Data 1 Data 2
TAG
Data
Data
S
TAG T
Data O
P
Data P
RF
SOF
Data 1 Data 2
Data
Data P
CRC
CRC
EOF
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