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208210A_UG_V1.6_ARFx3-PRO
Communication is always half-duplex. The radio transmission is priority over the radio reception (when the tran-
ceiver sends a radio frame, it is not capable of decoding an incoming radio frame).
Modem turnaround time: minimum time to meet before responding to a query.
Distant Modem
(customer)
Local Modem
(server)
Serial line
RF Link
query
query
answer
Turnaround time
≥100µs
All the data received on the serial link is packed into a radio frame. The format of the radio frame depends on the
protocol used.
When the unit operates as a transmitter and receiver, the transmission of radio frame always begins with the
following conditions:
Detection of a silence on the serial link (more than S217) after the receipt of the latest character.
Or when the number of characters received from the serial link is higher or equal to the maximum size of the
radio frame (S218).
5.2.1 Transparent mode
In transparent mode, the modem acts like a cable link. This means that alternately, the modem sends data
received from the serial link on the radio link and sends data received from the radio link on the serial link.
The format of the radio frame is:
•
<preamble><synchro> DATA <postamble>.
•
preamble, synchronisation and postamble are used for radio reception.
5.2.2 Addressed mode
In transmission mode, data received from the serial link is sent on the radio link with the following format:
•
<preamble><synchro><address> DATA <postamble>.
•
preamble, synchronisation and postamble are used for radio reception.
•
The Address field is initialised with the S256 value (LSB first).
5.2.3 In reception mode
The < Address> field in the radio frame is checked with the reception address (S252):
If the radio frame address corresponds to the transmitter-receiver reception address (S252), DATA (and only
DATA) is transmitted on the serial link.
Otherwise, the data received is ignored.
GB
