Schneider Electric 840 USE 106 0 manual System Scan Time

Theory of IEC HSBY Operation

System Scan Time

Effect on System The effect on system scan time of any Hot Standby system depends on how much

Scan Timestate RAM is going to be transferred from Primary to Standby. A Hot Standby system always has a higher scan time than a comparable standalone system.

The following has been done to provide information that allows you to forecast a Hot Standby system’s scan time:

Calculation of overall scan time for a normal Hot Standby baseline configuration

lcontaining minimum logic as a reference

Calculation of a PLC specific constant that expresses the increase of overall scan time related to an increase of memory to be transferred

The normal Hot Standby configuration state RAM contains:

In the local rack: power supply (CPS), PLC (CPU), RIO Head (CRP 93x), Hot Standby module (CHS)

In one remote IO drop equipped with 8 I/O modules, power supply (CPS) and

lremote adapter (CRA)

Only the logic for the scan time evaluation

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