On a few occasions now, when the <C> processor is rebooted while <R> <S> and <T> are in normal operation and the unit is stopped, sometimes a unit START signal is received in <RST> sequencing. Sometimes a Diesel start is sequenced. Could this be because the processor I/O is not establishing correctly in the allotted time and some inputs are being falsely seen? Has anyone else experienced this or is aware of the same issue. The unit did not start and the diesel did not start as all systems were locked off.
My first question would be: Why does <C> need to be re-booted so often?
Second, are there any discrete inputs to <C> for START or a Diesel Test?
Third, if all the system are locked out, it's hard to understand how a START could be initiated if the unit Master Control Mode was in OFF. Is the unit Master Control Mode in OFF when this occurs?
Fourth, is there a MODBUS link to the Mark IV? Does it include START or Diesel Test commands?
Fifth, is there <D> processor used to remotely operate the Mark IV?
I've never seen this issue, and it could be that for some reason the <C> I/O is not getting updated properly during the initiation of communication between <C> and <R>, <S> and <T>.
But, I suspect the answer to why <C> needs to be rebooted so often may be very telling....
Thanks for your input. The issue was being caused by the DCS. Basically the DCS was reading contact output information from <C> and taking action, which involved sending commands to <RST> contact inputs. Once that was understood the sequence was rewritten to prevent this happening. Its been like this for years apparently. Anyways its fixed now. <C> was not really being rebooted "frequently". Normal maintenance activity would be a more accurate statement.
Thanks again for your time.