Operating instructions

24 1892 1335 - Orion Radio Modem Operating Instructions - v2.9 / Aug 2009
USER DATA CONFIGURATION
Some User Data configuration may be relevant in Modes I and E as well as U, because User
Data may be carried beside telemetry in those modes.
Mode U Parameters
Unit ID
(ATS170)
The address of the unit. Since there is no distinction between Base and
Outstation for Data Only, UnitID may be any value from 0 to 254 provided
it is a unique address within the Group.
Dest ID
(ATS171)
The UnitID of the unit which will receive the data, hence 0 to 254. Pairs of
units normally have reciprocal UnitID and DestID, but this is not
mandatory. The special value 255 causes data to be broadcast to all
units within the group.
Group ID
(ATS169)
Any number between 1 and 254, all units the same within the Group. If the
special value of 0 is assigned, the unit ignores addressing and accepts
ALL messages. It also places a GroupID of 0 in its messages, which
causes ALL units (with the exception of repeaters) to accept the
messages without regard for addressing.
Over-air mode
(ATM0)
Mode U carries no telemetry, and therefore permits any of the four over-
air modes described on page 27.
Retries in
packet mode
(ATPRT)
Mode U in Packet (TP) over-air mode only: the number of retransmissions
of a packet without receiving an ack. (This does not raise a Comms
Alarm.)
User data
queuing
behaviour
(ATMTX)
(also applies to
User Data in
telemetry
modes)
To prevent undue delay on the one hand, or inefficiency on the other, you
can select the way data queues from three options:
v Start transmitting when first byte received in TX buffer. Stop
when buffer is empty and restart if another byte is received.
v Start transmitting when there is a gap in data input.
v If port baud rate is similar to or higher than over-air baud
rate, start transmitting when first byte is received in TX
buffer. If baud rate is lower, wait for a gap in data input.
See below for more detail on this mechanism.
More information about User Data queuing behaviour
ATMTX controls the behaviour of the Orion when it receives user serial data for transmission
on Serial Port A.
When set to Immediately, the transmission sequence is triggered as soon as a complete
byte is received in the transmit buffer. When the transmitter is ready and a preamble has
been sent, data begins to be transmitted. By this time, further data may be in the buffer – it
may even have become full and the sender flow-controlled. Transmission continues until the