ZHCS363L August 2011 – March 2017 TRF7970A
PRODUCTION DATA.
If the first command received by the RF interface defines the system as a passive target, then the receiver selects the appropriate data decoders (ISO/IEC 14443 A or ISO/IEC 14443 B reader or peer-to-peer) and framing option. Again, only the raw (decoded) data is forwarded to the MCU through the FIFO; SOF, EOF, preamble, sync bytes, CRC, and parity bytes are checked by the framer and discarded. The receiver works same as in the case of an active target.
The transmit system in passive target mode differs from active target and operates similar to the standard tag. There is no RF collision avoidance sequence, and encoders are used to code the data for ISO/IEC 14443 A or ISO/IEC 14443 B tag (at 106 kbps, to start) or peer-to-peer (at 212 kbps, to start) format. The coding system adds all of the SOF, EOF, CRC, parity bits, and synchronization bytes that are required by protocol. The response is transmitted over-the-air with a method known as load modulation.