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4-12 Series 90™-70 Enhanced Hot Standby CPU Redundancy User's Guide
–
May 2000 GFK-1527A
4
A fault is logged the first time SVCREQ #43 is used as a warning that the PLCs are not completely
synchronized.
The reverse data transfer, if any, is unaffected by this function block.
Enabling logic should be used with SVCREQ #43. A contact with a non-transferred reference
should be part of this enabling logic. That will allow the function block to be turned on/off directly
without being overwritten by the value from the active unit.
If the function block is invoked multiple times in a single sweep, the last call is the one that
determines the action taken.
Command Block for SVCREQ #43
The command block for the Disable Data Transfer Copy service request function block (SVCREQ
#43) is as follows:
Format Address
Disable Copies Selection Address +2
The first parameter is a word that represents the input parameter format for this Service Request. It
must be set to 0.
The second parameter is the word that specifies which data transfers to disable: Input and Output or
Output only. The valid values are:
Disable input and output copies 1
Disable output copy only 2
Successful execution occurs unless:
1. The Format parameter is non-zero
2. The Disable Copies Selection parameter is neither 1 nor 2.
3. The function block was invoked when the two units in a redundant system were not
synchronized.
4. The function block was issued on the active unit.
5. The CPU does not support the function block
Unsuccessful execution will not turn on power flow for the function block.