Counters

Sir
iwant to know why The counter up(CU) does not reset by itself after the preset value is reached,i mean to say that if i set KC20. the counter should become high to low when the preset value is reached,but it continues to stay high even after it reaches the value of 20 more over the counter becomes just after starting from zero though it sholud become high at 20 only what is the reason behind this.

To put it simply, so that you know that it got there.

Now please don't take this harshly, but with a counter, like every other command or function, it is really a lot more important that you know how it does behave rather than rattle on about how it ought to behave. So what does it matter whether it stays high or doesn't.

Either way, your programming needs for the counter will dictate how you use it. If you want it to work like you describe (immediate reset), use the output coil going high to reset the counter back to 0. If you want it to start at 1 rather than 0, use logic to preset the count back to 1.

If you know what you want and how your devices work, it becomes a simple matter of writing the logic you want.

Hope this helps,

Steve