Problem Restting The Counters In A Micrologix 1200

[BadgerGuy 0]

I added a reset to four of my counters but when I press reset, the counter resets to 1 and not 0 how can I get the counter to reset to zero? Thanks

[jstolaruk 9]

Use the cross-reference feature to find any and all pieces of logic that deal with that counter. Some other code is strobing it to count. If need be, post your program here and someone will be able to point it out. Edited 1 Feb 2006 by jstolaruk

[hakko808 0]

Check to make sure your counter presets are at 0 and not at 1.

[Guest]

smart money says that this post will help ... Edited 1 Feb 2006 by Ron Beaufort

[TConnolly 13]

If you reset a counter with the RST and the counter rung is true, it will immediately upcount the next scan. Be sure to see Ron's excellent explanation that he linked to to understand why this is the case. The quick and dirty solution is to go ahead and program a oneshot on the counter rung. Or you could structure your logic to avoid the situation.

[TimWilborne 108]

Or you can move a zero to the ACC instead of doing the reset. The counter will not increment if enabled

[keesoon 0]

If I move a "0" to the acc, the bits(DN,EN. etc.) change state?

[TimWilborne 108]

The CU bit will not go to zero like it will with a RES instruction According to Ron Beaufort in a previous post Edited 1 Feb 2006 by TWControls

[BadgerGuy 0]

I understant the rung is infact true in start up. Could I make the counters value -1 at first? thanks

[TimWilborne 108]

If the rung is true the ACC will be 1 on a RES and 0 on a MOV 0 to ACC

[TConnolly 13]

I believe that the pre-scan sets the counter CU bit when the program first runs at startup. This is supposed to keep an upcount from occuring if the rung is true on the first scan. If I'm wrong and the prescan is not setting the CU bit then you can specifically set it using the S:1/15 first pass bit just before you execute the CTU instruction. This will prevent the upcount and if the CTU rung is false then the CU bit will be automatically reset so everyting will be ready on the second scan. This is a superior solution because if the rung is ever not true on the first scan then you are stuck with a -1 in the ACC. Don't be afraid to manipulate the CU bit in your ladder. Understanding it and manipulating it when required can significantly increase the usefullness of counters in many applications. For example you can build self-aligning sequencers and for-next loops with counters by manipulating the CU bit. Edited 1 Feb 2006 by Alaric