4 |
Example
In the following example, when %M00035 is on, the input and output copies are disabled.
%M00035 |
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| %T00041 |
| MOVE_ |
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| INT |
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| REQ |
CONST | IN | Q | %L00001 | CONST | IN | Q | %L00002 | CONST | FNC |
00000 | LEN |
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| 00001 | LEN |
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| 00043 |
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| 00001 |
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| %L00001 | PARM | ||
Backup Qualification with SVCREQ #43
Service Request function block #43 can be used to help determine if the backup PLC unit is collecting inputs properly (that is, validate the input scan). It can also be used to help determine whether the backup PLC unit is calculating outputs and internal variables properly (that is, validate the logic solution). Instructions are given below.
Validating the Backup PLC's Input Scan
To determine whether the backup PLC is collecting inputs properly, follow these steps:
1.Activate SVCREQ #43 on the backup CPU, passing “0, 1" to disable the input and output data transfer copies.
2.Observe the backup unit's %I and %AI reference tables. The values in these tables correspond to the inputs that the backup is currently collecting.
3.Visually compare the backup unit's %I and %AI reference tables with the active unit's tables. Pay special attention to the %I and %AI references that are configured to be shared between the two units.
4.When you are satisfied that the backup unit is collecting inputs properly, disable the rung that calls SVCREQ #43.
Validating the Backup PLC's Logic Solution
To determine whether the backup PLC is calculating outputs and internal variables properly, follow these steps:
1.Activate SVCREQ #43 on the backup CPU, passing “0, 2" to disable the output data transfer copy.
2.Observe the backup unit's %Q, %AQ, %M, and %R reference tables. The values in these tables correspond to the inputs that the backup is currently calculating.
3.Visually compare the backup unit's %Q, %AQ, %M, and %R reference tables with the active unit's tables. Pay special attention to the %Q, %AQ, %M, and %R references that are configured to be shared between the two units.
4.When you are satisfied that the backup unit is calculating outputs and internal variables properly, disable the rung that calls SVCREQ #43.
| Chapter 4 Normal Operation |
