SLRC400 Datasheet, PDF (100/130 Pages) NXP Semiconductors – I·CODE Reader IC

Philips Semiconductors
I•CODE Reader IC
Product Specification Rev. 2.0 November 2001
SL RC400
16.4.2 RECEIVE COMMAND 16_HEX
Command _Codehex
Action
Receive
16
Activates Receiver Circuitry
Arguments and Data
-
Returned Data
Data Stream
The Receive-Command activates the receiver circuitry. All data received from the RF interface is returned via
the FIFO buffer. The Receive-Command can be started either by the µ-Processor or automatically during
execution of the Transceive-Command.
Note: This command may be used for test purposes only, since there is no timing relation to the Transmit-
Command.
16.4.2.1 Working with the Receive Command
After starting the Receive Command the internal state machine decrements the value set in the RxWait-
Register with every bit-clock. From 3 down to 1 the analog receiver circuitry is prepared and activated. When
the counter reaches 0, the receiver starts monitoring the incoming signal at the RF-interface. If the signal
strength reaches a level higher than the value set in the MinLevel-Register it finally starts decoding. The
decoder stops, if no more signal can be detected on the receiver input pin Rx. The decoder indicates
termination of operation by setting bit RxIRq.
The different phases of the receive sequence may be monitored by watching ModemState of the
PrimaryStatus-Register (see 16.4.4).
Note: Since the counter values from 3 to 0 are necessary to initialise the analog receiver circuitry the
minimum value for RxWait is 3.
16.4.2.2 RF-Channel Redundancy and Framing
For ISO 15693 the decoder expects a SOF pattern at the beginning of each data stream. If a SOF is
detected, it activates the serial to parallel converter and gathers the incoming data bits. For I•CODE1 the
decoder do not expects a SOF pattern at the beginning of each data stream. It activates the serial to parallel
converter with the first received bit of the data. Every completed byte is forwarded to the FIFO. If an EOF
pattern (ISO15693) is detected or the signal strength falls below MinLevel set in the RxThreshold Register,
the receiver and the decoder stop, the Idle-Command is entered and an appropriate response for the µ-
Processor is generated (interrupt request activated, status flags set).
If bit RxCRCEn in the ChannelRedundancy Register is set a CRC block is expected. The CRC block may be
one byte or two bytes according to bit CRC8 in the ChannelRedundancy Register.
Remark: The received CRC block is not forwarded to the FIFO buffer if it is correct. This is realised by
shifting the incoming data bytes through an internal buffer of either one or two bytes (depending on the
defined CRC). The CRC block remains in this internal buffer. As a consequence all data bytes are available
in the FIFO buffer one or two bytes delayed.
If the CRC fails all received bytes are forwarded to the FIFO buffer (including the faulty CRC itself).
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Preliminary