Chapter 4. CPU OperationGFK-2222AD April 2018 1494.5 Run/Stop OperationsThe PACSystems CPUs support four RUN/STOP Modes of operation. You can change these modes in thefollowing ways: the RUN/STOP Switch, configuration from the programming software, LD function blocks,and system calls from C applications. Switching to and from various modes can be restricted based onprivilege levels, position of the RUN/STOP Switch, passwords, etc.Mode OperationRun/OutputsEnabledThe CPU runs user programs and continually scans inputs and updates physicaloutputs, including Genius and Ethernet outputs. The Controller and BackplaneCommunications Windows are run in Limited, Run-to-Completion, or Constantmode.Run/OutputsDisabledThe CPU runs user programs and continually scans inputs, but updates to physicaloutputs, including Genius and Field Control, are not performed. Physical outputs areheld in their configured default state in this mode. The Controller and BackplaneCommunications Windows are run in Limited, Run-to-Completion, or Constantmode.Stop/IO ScanEnabledThe CPU does not run user programs, but the inputs and outputs are scanned. TheController and Backplane Communications Windows are run in Run-to-Completionmode. The Background Window is limited to 10ms.Stop/IO ScanDisabledThe CPU does not run user programs, and the inputs and outputs are not scanned.The Controller and Backplane Communications Windows are run in a Run-to-Completion mode. The Background Window is limited to 10ms.Note: STOP Mode I/O scanning is always disabled for redundancy CPUs.Note: You cannot add to the size of %P and %L reference tables in RUN Mode unless the %P and%L references are the first of their type in the block being stored or the block being stored isa totally new block.
