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RF54
User Guide
Transceiver mode
The transceiver mode used a secured addressed protocol.
The communication is always half-duplex. The radio transmission is processed
prior to the radio reception. When the transceiver is sending a radio packet, it
is not able to decode any incoming radio packet.
If no data are sent on the serial link, the modem is waiting for radio
reception. Each radio packet sent by another modem is received and the
validated data extracted from the radio packet are sent on the serial link.
All the data received on the serial link are encapsulated in a radio packet.
In transmission mode, data received on the serial link are sent on the radio
link with the following format:
<Preamble><synchro><packet header> DATA <CRC><postambule>.
Preamble, synchronisation and postambule are used for the radio reception.
The packet header contains the following fields : packet length, number of
retries and packet number, target address.
The CRC follows the data and check the integrity of the radio packet.
The Target Address field is set up with S256 register. The Target Address
value 0000 is a broadcast address.
In reception mode: The <Target Address> field of the radio packet is
checked (if different of 0000) with the reception address (S252).
If the radio packet address matches the transceiver reception address (S252),
DATA (and only DATA) are transmitted on the serial link
Otherwise received data are silently discarded.
Transceiver state machine
When operating in transceiver mode the 'RF transmission' state machine is:
Idle state of the transceiver : by default the transceiver is waiting for
incoming data on the RS232 link and for incoming radio packet on the radio
link. Processing incoming RS232 data : the incoming RS232 data are
internally buffered. The buffered data are encapsulated in a radio packet and
transmitted. Processing incoming radio frame : the valid data are
extracted from the incoming radio packet and internally buffered. The
buffered data are sent on the fly to the RS232 module output.
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