Operating instructions

1892 1335 - Orion Radio Modem Operating Instructions - v2.9 / Aug 2009 25
buffer is empty, which may either be because there is no more data, or, in the case of a slow
source, because transmission has outstripped the input. If a further byte appears in the buffer,
the process is repeated.
When set to End of Message, the transmission sequence is triggered by a break in the User
Data input. This may be because the message has ended, or because the sender has been
flow-controlled to avoid buffer overflow. As soon as the transmitter is ready and a preamble
has been sent, the data in the buffer begins to be transmitted. Transmission continues (with
flow control if necessary) until the buffer is empty, which may either be because there is no
more data, or, in the case of a slow source, because transmission has outstripped the input. If
further data appears, the process is repeated when there is a break in it.
When set to Baud Rate Dependent, one of the behaviours above is chosen on the basis of
the relationship between Port A baud rate and the over-air baud rate. If Port A baud rate is
similar to or higher than the over-air rate, the first behaviour is followed (Immediate); if the Port
A rate is lower than the over-air rate, then the second behaviour is followed (End of Message).
v Flow control can be disabled, but data will be lost if buffer capacity is exceeded.