I'm trying to find a way to prevent a PV displaying a change of state that isn't being acted upon in the (L32E) plc.
I have 5 interlocked buttons that write 1,2,4,8 or 16 to a tag in the plc. The first five bits in the tag are then used to enable outputs in 5 rungs which each have their own respective interlock bits.
If all conditions per rung are met, the output will be enabled. Fine.
If the conditions are not met for a given rung, the output bit will not be enabled but the array of buttons will change it's indicating state from one to another all the same because the new value has been written to the plc. This is what I'm trying to prevent.
First thought was to place a MOV in parallel with the output bit per rung to hold the value in the tag and freeze the displayed button value, but that wouldn't work: Even if the new "target" rung's conditions are all met, the pv would get a message back from the plc that the previous value is held and would be re-written with that value, so nothing would change. (Or would that only be the case when trying to change from the last of the five rungs in scan-order?) Either way, that's a non-starter.
To one-shot the MOV would be the same as the pv is doing anyway. The animation on these buttons is limited to visibility so nothing doing there as they form part of a graphic representation and need to remain visible.
Stumped!
I have 5 interlocked buttons that write 1,2,4,8 or 16 to a tag in the plc. The first five bits in the tag are then used to enable outputs in 5 rungs which each have their own respective interlock bits.
If all conditions per rung are met, the output will be enabled. Fine.
If the conditions are not met for a given rung, the output bit will not be enabled but the array of buttons will change it's indicating state from one to another all the same because the new value has been written to the plc. This is what I'm trying to prevent.
First thought was to place a MOV in parallel with the output bit per rung to hold the value in the tag and freeze the displayed button value, but that wouldn't work: Even if the new "target" rung's conditions are all met, the pv would get a message back from the plc that the previous value is held and would be re-written with that value, so nothing would change. (Or would that only be the case when trying to change from the last of the five rungs in scan-order?) Either way, that's a non-starter.
To one-shot the MOV would be the same as the pv is doing anyway. The animation on these buttons is limited to visibility so nothing doing there as they form part of a graphic representation and need to remain visible.
Stumped!