User's Manual

Chapter Three Operation
man_905_2.1.doc Page 23
to attempt to transmit to the remote module every ten minutes. For critical applications, this status
can be configured to be reflected to an output on the module for alert purposes. The outputs on the
module may also be configured to reset after a specified timeout (digital outputs reset to “off”,
analogue outputs reset to 0 mA) allowing the system to turn off in a controlled manner e.g. a pump
will never be left running because of a system failure.
Example of Successful Communications
Local Unit
• Listen to ensure channel is clear
Remote Unit
• If clear, transmit message
TX LED flashes if radio
RX LED flashes if RS485
• Receive message
RX LED flashes
Check message for integrity
• RX LED flashes
• Acknowledgement
received okay -
communication complete
• If message okay, transmit it back
as acknowledgement
TX LED flashes if radio
RX LED flashes if RS485
Outputs updated as per
message received.
Example of unsuccessful communications
Local Unit
• Listen to ensure channel is clear
Remote Unit
• If clear, transmit message
TX LED flashes if radio
RX LED flashes if RS485
• Receive message
RX LED flashes
Check message for integrity
Message corrupted - do
nothing
• No acknowledgement received
• Retry up to four times
• Still no acknowledgement
“Comms fail” status to remote unit
set
If status is mapped to an output,
set output
• If no update received for an
output within watchdog timeout,
check to see if the output is
configured to reset
• Reset outputs if configured
(4)