How high, high speed input required?

[OkiePC]

I believe there is only one HSC on the ML1100. It can be assigned to one of the four high speed inputs.

You are not the first programmer to be confused by this.

I have not used one of those units, I am just repeating what I have read in earlier posts on this subject.

There are a bunch of LONG discussions at MrPLC.com. (Search "HSC 1100".) In those threads there are methods described that allow you to use more than one of the high speed inputs by using input driven interrupts instead of the HSC.

Here's one of them:

http://forums.mrplc.com/index.php?showtopic=6520&hl=

Hope this helps...
Paul

 

[Ken Roach]

The confusion seems to be the difference between high-speed Inputs and high-speed Counters.

On the MicroLogix 1100 and 1200, Inputs 0,1,2,3 are wired into a faster input circuit than the other Inputs on the controller.

Those inputs can be configured and used as pulse catching (latching) inputs, as high-speed interrupts, as inputs for the Programmable Limit Switch (PLS) function or as inputs to the High Speed Counter (HSC) function of the controller.

The High-Speed Counter function includes the high-speed input circuitry, the high-speed counter hardware and the firmware and user instructions that configure and operate that hardware.

There are four input points wired to the HSC hardware to support a quadrature encoder input with external reset and hold inputs. Even if you only use a single counter channel, the other inputs are still wired to a single high-speed counter hardware circuit and the MicroLogix 1100 and 1200 do not support multiple HSC functions.

 

[Ken Roach]

I see my contemplation has cost me the post race.....

Although I've used event interrupts for fast counting, I think they're the wrong solution for accurate frequency measurement.

 

[OkiePC]

I see my contemplation has cost me the post race.....

No, Ken, I think your contemplation has, yet again, resulted in an authoritative response that will help clear the mud for other readers (including me!)

Thanks...

 

[timbo_uk]

Ken and Okie, thanks for the link going through it now (got to stop thinking about work when at home!)