User manual

Chapter Three Operation
man_905-105_2.9 Page 25
3.1.1 Communications
If transmissions are not successful (radio or serial), then the module will re-try up to four times at
random intervals to transmit the message.
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
)