Timer Inside Subroutine

I am trying to use a TOF function inside of a subroutine for a MicroLogix 1200. However, as soon as I download the program and the PLC starts to scan, the accumulated value immediately jumps up to the preset value, despite the conditions not being met for it to begin timing. If I put a first scan timer reset in the main program, the timer will never start.
Any ideas?
Thanks

I might be wrong for your application but I would suggest ladder logic plus a TON outside the subroutine and trigger it when necessary when the subroutine is called.

Welcome...Read up on the TON, it may be more of what you're looking for. This is a WAG since I don't know what the timer is intended to do.
HTH

Never use the TOF...well almost never. It is just counter intuitive that the timer starts out DN and then stays DN until a preset amount of time after the timer instruction goes false.

In a very few cases using a TOF in place of a TON, can clean up a messy rung, but in 99.9% of cases, the TON will do what you need it to do and be easier to write and follow.

To the OP, you need to read up on the TOF. It is doing exactly what it is supposed to do. It starts with the ACC = PRE so it doesn't start timing automatically on a power cycle. Since it begins timing when it is false it needs to see a TRUE to FALSE transition.

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Okie this is not intended to teach you, I know you know what you are doing! This is just for public consumption.

I do use the TOF and the TON. It's actually real simple and believe it or not they work almost identically.

First thing I ask, "Do you want to make something happen FOR a duration or AFTER a duration".

FOR a duration means you want to use the TT bit and while either timer can work I always use a TON.

AFTER a duration means you want to use the DN bit. Then the next question is do you want to turn something ON or OFF after a duration. That answer tells you which timer to use.

If you want to turn the DN bit on, make the rung true. If you want to turn the DN bit off, make the rung false. It works the same for both types of timers. The difference is in where the delay factors in. Do I delay turning on (TON) the DN bit and some associated output, or do I want to delay turning off (TOF) the done bit and some associated output.

I have seen people struggle and waste far too much time pushing a square peg into a round hole.

OG