RSLogix 500 - I cannot change timer preset value

I'm trying to simply change a timer preset value from 100 to 500 (x .01 sec) using RSLogix 500. It allows me to highlight the value and type in the new value, but when I hit enter, it reverts back to the original '100' value.

I've tried making this change on the ladder code screen as well as the 'Timers' table, with the same result.

For troubleshooting purposes, I proved that I could successfully change several other timers, but this particular one doesn't permit a change.

Any suggestions? Maybe I should just re-write the line of code.

Thanks in advance,
Tom

Is there somewhere else in the program (or a hmi) thats writing to your timers preset (Txxx.PRE) ?

I'll check. It could be that the timer value is dependent on a switch position elsewhere in the logic. I'll let you know.

Problem solved. Elsewhere in the code, I have a MOVE statement that moves the timer preset value to the line that I was trying to change (depending on a switch position). That's why it wasn't accepting my manual change.

Thanks for your help This help forum is great.
-Tom

teppe said:

Problem solved. Elsewhere in the code, I have a MOVE statement that moves the timer preset value to the line that I was trying to change (depending on a switch position). That's why it wasn't accepting my manual change.

Thanks for your help This help forum is great.
-Tom

Click to expand...

To be pedantic and precise, your RSLogix500 software was making the change to 500, so your highlighted statement above isn't technically correct.

The value you entered was being set into the timer preset register, but your code at some point in time later was re-writing it back with your MOV instruction. So there was a finite time when the preset value was at 500.

The reason I make this distinction, to give warning, that there might, possibly, be code elsewhere that inspects this preset value, perhaps (for example) to enable another function if the preset is greater than 250..... Your manual input of that higher value may "trigger" unwanted actions.

The warning is issued with regard to safety, personnel and machine or process "damage" - it is not wise to go poking values into any data-table locations without a full understanding of the implications, and an assessment of whether the changing of a value will cause problems should be made.

Your Cross-Reference facility will be your friend here - you can use it see where any references to that data-table value is made in the program.

This is especially true if you, personally, didn't write the whole program, and even if you did, you may have forgotten that you used such-and-such a value to do something else.

daba said:

...and even if you did, you may have forgotten that you used such-and-such a value to do something else.

Click to expand...

Been there. Done that.