CR14 Datasheet, PDF (32/46 Pages) STMicroelectronics – Low Cost ISO14443 type-B Contactless Coupler Chip with Anti-Collision and CRC Management

7 Tag access using the CR14 coupler
CR14
Figure 29. 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
TAG
Data
Data 1 Data 2 Data
S
TAG T
Data O
P
Data P
RF
SOF
Data 1 Data 2
Data
Data P
CRC
CRC
EOF
Figure 30. Standard TAG Command: Complete TAG Access Description
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Device
Select I/O Request Request
I²C Code Register Frame Frame
Write Address Length Bytes
Device
Select
Code
Read
Answer
Frame
Length
Request
Frame
Bytes
START
STOP
START
STOP
SOF
EOF
SOF
EOF
Request
TAG
RF
Frame CRC ^{T0 T1} Answer Frame CRC
Characters
<--> <--> Characters
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7.2 Anti-Collision TAG Sequence
The CR14 can identify an ST short range memory using a proprietary anti-collision system.
Issuing an I²C Write command to the Slot Marker Register (Figure 16) causes the CR14 TO
automatically generate a 16-slot anti-collision sequence, and to store the identified Chip_ID in
the Input/Output Frame Register, as specified in Table 5.
After receiving the Slot Marker Register I²C Write command, the CR14 generates an RF
PCALL16 command followed by fifteen SLOT_MARKER commands, from SLOT_MARKER(1)
to SLOT_MARKER(15). After each command, the CR14 waits for a tag answer. If the answer is
correctly decoded, the corresponding Chip_ID is stored in the Input/Output Frame Register. If
there is no answer, or if the answer is wrong (with a CRC error, for example), the CR14 stores
an error code in the Input/Output Frame Register. At the end of the sequence, the host has to
read the Input/Output Frame Register to retrieve all the identified Chip_IDs.
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