166 ControlEdge HC900 Process & Safety Controller User and Installation Manual Revision 10
May 2019
Warm Start
A Warm Start is a restart of the control strategy using dynamic data that is stored in battery backed RAM
to allow control action to resume exactly as it was before the restart. In the Warm Start procedure
(flowcharted in the main flow of Figure 95), diagnostic testing proves the integrity of the hardware,
software, and configuration database resulting in an automatic Warm Start of process control. Control
action is resumed exactly as it was before the outage.
This flowchart also indicates actions that would be taken by the controller in case of fault. Notice that if
primary diagnostic testing determines that RAM or firmware is faulty, all process control functions cease,
and the Status LED (red color) strobes one blink, periodically. If RAM and firmware tests pass, but the
database in RAM is faulty, the controller initiates the Cold Start operation.
Figure 95 – Warm Start Operation
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