Tele PL7 Drum Controller instruction

Hello everyone,
I'm currently writing a program for a Tele PSX-57302 Premium PLC using PL7 Junior programming software. I just discovered that I am not able to directly write to a up/down counter accummed value (.v in tele jargon). So, I did a little digging and have decided to use a "Drum Controller" to step through machine sequence steps.

Here are my questions. Can anyone tell me what happens when I complete the last configured step of the drum controller. Does it reset to "step zero" on the next pulse of the "step up" input, or do I have to reset the drum controller myself? None of the
books I have, nor the help section of the software, tell me what I need know. Also, I don't understand the time function of the instruction. I'm assuming that the drum controller has a "built in" timer that I can use to advance to the next step, after being in the prior step for a set period of time. Am I correct in this assumption?

Thanks for any and all help.

Jeff

Drum Controller

Hi Jeff,

I have a reference manual (TLX DR PL7 12E) that decribes the drum controller function block in great detail. It is listed on page 2/9 of this manual. I am not sure with what your trying to do with your application but when the drum contoller reaches the last step you have to reset the drum contoller. This is done with the return to zero input. If you need i could scan this document and either e-mail or post it. Good luck to you.

Telemecanique PL7

You are correct, the counter value %Ci.V can not be written to. Have you thought of making your own counter using operate blocks to increment and comparison blocks to decode?

The PL7 drum controller "rolls over" to step 0 if another pulse is detected at input U when at the final step. You need to implement logic to stop the drum, the same way you need to stop a normal counter from rolling over.

The drum variable %DRi.V is an internal elapsed timer (time base = TB) which you can use in your logic for monitoring the length of time each step has been enabled.

Thanks guys,
I do appreciate the help.

Jeff