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Rev. 1.20
77
October 28, 2020
BC45B4523
Position
CollPos Value
Comment
SOF
0
CollErr, FramingErr are set
1st bit of 1st byte
1
CollErr is set
2nd bit of 1st byte
2
8th bit of 1st byte
8
Parity of 1st byte
8
CollErr, ParityErr are set
1st bit of 2nd byte
9
CollErr is set
7th bit of 2nd byte
15
Parity of 2nd byte
16
CollErr, ParityErr are set
Example of Collision Position and Reported Value of CollPos
Bit-Oriented Reception in ISO14443A
During anti-collision process in ISO14443A, the first received byte may be partially transmitted from the card.
For reception of such split byte, RxAlign in the BitFraming register defines the first received bit position in the
first decoded byte. The following figure shows the evaluated data byte when setting RxAlign to different values.
Assume that the bit ParityEn equals to 1, if RxAlign is not equal to zero, the parity of the first byte is not checked.
RxAlign = 0
0
SOF
1
1
0
1
0
1
0
1
1
0
1
1
0
0
1
1
0
Receiving Pattern
0
1
1
0
RxAlign = 1
Par
“56”
“F4”
RxAlign = 5
0
1
1
0
1
0
1
0
1
1
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
1
0
1
1
0
0
1
1
0
0
1
1
0
“AC”
Par
Par
Par
“E5”
0
1
1
0
1
0
1
0
1
1
0
1
1
0
0
1
1
0
0
1
1
0
Par
Par
“C0”
“95”
Par
“CF”
Example of Evaluated Data for Different RxAlign Settings
Error in Reception
At the end of reception, some errors in reception are indicated via the error flags in the Error register. The meaning
of the error flags related to the reception is described as follows.
Error Flag
Event
FramingErr
Invalid frame format, namely
– SOF and EOF do not conform to the standard defined in the receiver.
– EGT in ISO14443B is incomplete.
ParityErr
Wrong parity is received in ISO14443A
CRCErr
Wrong CRC is received
CollErr
Collision is detected in ISO14443A and ISO15693
Error Flags Related to RF Reception
EMD Suppression
Conventionally, to handle frame containing EMD, microcontroller must consider received frame if it is EMD by
relying on interrupt signal after end of reception and already-received data in FIFO. Although, the RxMultiple
bit or Receive command can assist this operation, such operation takes significant time from transaction between
microcontroller and the device via SPI. Then, response time is quite long.
The device contains EMD suppression function, which is a feature designed to reduce microcontroller task in
handling EMD frame reception. When bit EMD_Suppress (Sector0-0x1F.1) is set, if the number of received data
byte is less than 3 bytes and frame contains errors related to reception, namely CRCErr, FramingErr, ParityErr,
CollErr, system will automatically discard the received data and returns to “RxAwaiting” state to receive next
frame as shown in the State diagram presented in the “State Machine” section. If the number of receiving byte is