VWA00: Preselection changed during redundancy switch-over
A description of this resolution:
- Amending the function block circuit
To guarantee correct redundancy balancing, swap the first adder (1 input) for the editor module ZAE in the function block circuit VWA00 in the module V_ZAE sheet 1/5 and then configure as follows:
Configure the label input variable to the start value STW of the counter (ZAE parameter 12).
Set the ZAE parameter ‘RES stat’ (ZAE parameter 08) to a constant '1'.
Configure the output ZL (ZAE parameter 17) as the multi-variable $ 'VORW'.
This error occurs in function block circuits up to and including Version A:01.08.90 .The amended function block circuit has Version A:01.02.93.
"VWA00: Preselection changed during redundancy switch-over" resolves the following:
- Service Station
Redundancy balancing of the function block circuit preselection VWA00 does not work.
After redundancy switch-over, error acknowledgement and subsequent resetting of the CMX 40, the preselection is set to zero.
This problem only affects programs in redundant CMX40 modules and only after second redundancy switch-over, if no set command (S1-Sn) was given before.
The underlying cause is:
- Values not updated during redundancy adjustment
In the preselection integer values are stored in IF structures. If, as the result of a failure, a redundancy switch-over is carried out, reset will set these stored values to zero in the passive CMX.
In the cyclical redundancy balancing, the values that are set to zero are not updated by the active CMX. As a result, any further redundancy switch-over is not bumpless.