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5.6 Online Program Change for Redundancy
5.6.2 Program Change While CPU is Running
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3) Changing programs being accessed by the other GX Developer online
The error dialog box in Diagram 5.75 will appear if online program change is
executed to the CPU module during system switching or operation mode
change:
4) Online program change to CPU module during system switching or
operation mode change
The error dialog box in Diagram 5.76 will appear if online program change is
executed during memory copy from the control system to the standby system:
(g) Online program change in Separate Mode
In the separate mode, online program change is executed only to the system that
specified in the target connection settings.
Online program change is not executed to the CPU module of the system that is
not specified in the target connection settings.
(h) Extension of scan time due to online program change
If online program change is executed, the control system CPU module scan time
will extended.
Refer to the following manual for information on control system CPU module scan
time extension:
QCPU User's Manual (Function Explanation, Program Fundamentals)
(i) Signal Flow Processing
The signal flow in the changed steps or program turns on.
Therefore, if a running program is changed online, the rise, fall and SCJ
instructions will do the following:
1) Rise instruction (PLS instruction, P instruction, SP. instruction)
Even if the execution condition changes from off to on when online program
change is complete, the rise instruction will not be executed.
It will be executed when the execution condition is turned off and on again.
2) Fall instruction (LDF, ANDF, ORF, MEF, PLF)
If the execution condition is off when online program change is complete, the
fall instruction will be executed again.
3) SCJ instruction
If the execution condition is on when online program change is complete, a
jump to the specified pointer will be executed without waiting 1 scan.
Diagram 5.75 Error Dialog Box Displayed on GX Developer
Diagram 5.76 Error Dialog Box Displayed on GX Developer