bernie_carlton
Lifetime Supporting Member + Moderator
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.
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.