GX developer: Why is M32 zero?

[Mas01]

Why is M32 zero when all the conditions for setting are met? Thanks in advance.

 

[parky]

This is because it is a pulse instruction, it is only true when the logic in front of it goes from false to true and is only on for one scan of the program, you are unlikely to see it while monitoring perhaps about 1 in 5 chances the coms reads it when it is true.
effectively it is a one shot, when all 4 contacts are false (in this case as they are N/C) then M32 will be on for one scan of the program.
so for example if any one of the 4 contacts (inputs in this case) goes true then back to false M32 pulses for one scan.
This can be a little confusing as it will not need all 4 contacts to go to true then false for it to work the following is true.
all 4 are off (initial condition) it will pulse M32 once.
If one goes true nothing happens
If the other 3 are false & the one goes back to false then M32 pulses.
if two go true & only one of them goes false nothing happens & so on.
What it needs to see is a transition from a false to true before M32 pulses,
It appears the inputs are tank level controls so when all 4 are false (assuming these go false on the different levels), then the last one to go off will be low level & it creates a pulse for some sort of control perhaps stops a pump or something.

 

[AlfredoQuintero]

Because the "PLS" prefix in the coil means that when the coil changes from non-energized state to energized state, the bit addressed in the coil will be TRUE for just one scan. After the next scan it will change to FALSE.


Edit: parky you bit by a few seconds and with a much better reply...

 

[Mas01]

This is because it is a pulse instruction, it is only true when the logic in front of it goes from false to true and is only on for one scan of the program, you are unlikely to see it while monitoring perhaps about 1 in 5 chances the coms reads it when it is true.
effectively it is a one shot, when all 4 contacts are false (in this case as they are N/C) then M32 will be on for one scan of the program.
so for example if any one of the 4 contacts (inputs in this case) goes true then back to false M32 pulses for one scan.
This can be a little confusing as it will not need all 4 contacts to go to true then false for it to work the following is true.
all 4 are off (initial condition) it will pulse M32 once.
If one goes true nothing happens
If the other 3 are false & the one goes back to false then M32 pulses.
if two go true & only one of them goes false nothing happens & so on.
What it needs to see is a transition from a false to true before M32 pulses,
It appears the inputs are tank level controls so when all 4 are false (assuming these go false on the different levels), then the last one to go off will be low level & it creates a pulse for some sort of control perhaps stops a pump or something.

Yes, it is used to control the sump pump on line 986. The sump pump (as the name suggests) is at the bottom of the tank for pumping the water around the system & when the level is low, startup is inhibited to prevent pumping air which would damage the pump.

 

[Mas01]

Because the "PLS" prefix in the coil means that when the coil changes from non-energized state to energized state, the bit addressed in the coil will be TRUE for just one scan. After the next scan it will change to FALSE.


Edit: parky you bit by a few seconds and with a much better reply...

Many thanks AlfredoQuintero