Interrupts on a CPU 313C-2 DP

Hi,
I'm currently using the above processor on a job that requires counting 4 of the inputs at about 235Hz. At the moment I'm missing pulses so I would like to use the interrupt capability of the CPU.

In the hardware config I have checked the box "Rising Edge" ,for example input bit 0 (see attached image), but I don't know what OB the process will jump to. How do I set this or find it out?

Thanks,
Matt

It's been a while for me with the Siemens stuff and I've never had a chance to work with the 313C. However, with the 315, there is a single hardware interupt OB (OB43 I think?). When a hardware interrupt occurs the OB will automatically run. One of the data words in the OB declaration contains a mask indicating the source of the interrupt. Save this information and move on.

Do as little in the interrupt as you can get away with. You don't want to extend the interrupt time so long that you miss another event. If the events are fixed to each other this probably isn't a concern. But if the events are random you still might have an issue.

Also, a 235 Hz signal only gives you about 2msec of on time (assuming a 50% duty cycle; things only get worse fromn there). Can your input points consistently respond that fast?

Keith

The h/w interrupt triggers OB40 for the 313C:

Yes, OB40. But CPU313 has two counting inputs. (they are handling with SFB47, see also similar 46 48)

You need in four inputs, so, may be it is possible to organize hardware time-division multipexing of counting inputs?

Thanks, I'll look into that. I'm also considering the possibilty of using an FM 350-2 Counter Module which would definitely sort the problem but with a price tag!