Mitsubishi F1 series counter question.

I'm translating a printout of a program written for an F1/F2 series Mitsubishi PLC to a Micrologix.

I've stumbled upon something that I can't find the answer to in the Mitsubishi manuals.

In the Mitsubishi PLC there was a very simple line:

LD M73
OUT C66
K50

From what I can gather, the M73 is a 10ms pulse bit, and the C66/K50 is just a counter with preset 50.

My only question is, what happens in the Mitsubishi processor when a counter is "done" but is not reset, does its register continue counting? This counter is not being reset until sometime later in the program, and it appears that it can be "done" for a few minutes, or longer, before being reset.

With the Micrologix, the counter keeps counting and eventually the accumulator value rolls over. But I don't know what happens with the Mitsubishi F1/F2 counter's register value once it is done, but doesn't get reset.

I think they were using counters and the M72/M73 time bits to create timers to delay actions. Which I will probably end up actually going through and replacing them all with timers instead. They did this multiple times throughout the program, but this one is the only counter that didn't have any permissive other than the timing pulse, so it was free running that counter the whole time the program was running.

Thanks

Not sure about this but from memory I think C66 does not energise untill it has reached the preset value, in this case 50, It will not carry on counting and will reset when commanded to. So M73 will need to go on and off 50 times before you get the out C66. Hope this helps.

Yes. And the M73 is going on/off every 10ms, (5 on, 5 off). So it's basically a Retentive timer in RSLogix with a preset of 50 and a base of "0.01" seconds.

I was just curious what the register value of the counters in the Mistubishi PLC did when it reached the set value, was not reset, but still was told to count (on/off transitions).

The count will be benign once the value is reached, of this I am sure.

Benign, that's a word I don't read often. Must be a cultural thing. Threw me for a loop cause I read "be benign" as "begin" at first.

But I understand, thanks.