Simple timer reset RS5000

Let's start with the end of the scan which produces the true of Timer[1]/DN (the circled point in your timing diagram.

Now go to the first scan after that. In the first rung the NC of Timer[1]/DN (which at this point is still true) causes the part of the rung following to be false. Thus Timer[0]/EN is now false. This causes EXACTLY the same reaction in the timer as your use of the RST in your first post. Timer[0].ACC goes to zero and Timer[0]/DN becomes false.

Since Timer[0]/DN is now false then the second rung is false leading into Timer[1]. Thus Timer[1] is also reset (Accumulator = 0, DN bit becomes false)

Now we go to the second scan after. Now because Timer[1]/DN is false the NC contact is true and the rung leading into Timer[0] is true. So it is re-enabled and begins timing just as at the beginning of your timing diagram.

To be a true representation at the right side of your timing diagram you would show Timer[1]/DN as being true for ONLY ONE SCAN TIME. Similarly on the top line of your timing diagram Timer[0]/EN will be false FOR ONLY ONE SCAN TIME.

A really good trick is to add some counters in different places in your code, so you can see what i s actually going on, place a counter or great a DINT tag for each RUNG and Branch, use the add option to add 1 to each DINT tag on each rung and branch this will show what is actually going on.

TONs are an instruction that reset themselves when their permissives (the logic on the left) is no longer true.

So starting from the moment T1 completes:
1. T1.DN bit in rung 0 becomes false (as it's an XIO)
2. T0 resets its accumulator to 0.
3. T0 XIC in rung 1 becomes false as the T0 timer is no longer DN.
3. T1 resets its accumulator to 0.
4. T1.DN bit in rung 0 becomes TRUE (as it's an XIO and T1 has reset)
5. T0 begins to count again.

Again, this is all happening in the matter of a few scans, so you won't be able to see it. You just have to break the process up into single steps mentally to understand what is happening.

Edit: just saw Bernie already answered this, was doing a quick reply from page 1. Haven't had my caffeine yet

Holmux said:

A really good trick is to add some counters in different places.

Click to expand...

I do this in conjunction with the one second tick to replace timers.