Rainbow Electronics AT88RF1354 - Manual (Page 29)

13.56 MHz Type B RF Reader
29
8547A −RFID−10/08
A.5. Card Data Transmission
The PICC waits silently for a command from the PCD after being activated by the RF field. After receiving a valid
command from the PCD, the PICC is allowed to turn on the subcarrier only if it intends to transmit a complete
response frame. The PICC response consists of TR1, SOF, several bytes of data followed by a 2 byte CRC_B, and
the EOF. The subcarrier is turned off no later than 2 ETUs after the EOF. Figure A-4. show the PICC frame format.
When the subcarrier is turned on it remains unmodulated for a time period known as the synchronization time (TR1).
The phase of the subcarrier during TR1 defines a logical one and permits the reader demodulator to lock on to the
subcarrier signal. The subcarrier remains on until after the EOF transmission is complete.
Figure A-4. Format of a frame transmitted by the PICC to the reader.
Transmit Data and CRC_B
Data Transmission
Subcarrier On Subcarrier Off Subcarrier Off
TR1 SOF EOF
A.6. Response Timing
After the PICC receives a command from the PCD, it is not permitted to transmit a subcarrier during the guard time
(TR0). The minimum guard time is 8 ETUs for all command responses. The maximum guard time is defined by the
frame waiting time (FWT), except for the ATQB response (response to REQB or Slot MARKER polling commands)
which has a maximum TR0 of 32 ETUs.
Figure A-5. ISO/IEC 14443 response timing requirements for the card.
Reader/Writer
PICC (Chip)
CRC EOF
Subcarrier OFF Subcarrier ON
No Modulation
TR0 TR1
Data
SOF Response
Unmodulated Carrier
The FWT is the maximum time that a PICC requires to begin a response. The PICC transmits a parameter in the
ATQB response to the polling command that tells the reader the worst case FWT. The PCD is not permitted to
modulate the RF field while waiting for a PICC to respond to a command. Modulation of the RF field during a PICC
memory read or write operation may corrupt the operation or cause reset of the PICC.