Micrologix Processors - is one faster than the other?

Hi Everyone,

I am trying to choose a Micrologix PLC for an application. Apart from the number of I/Os, is there any difference in them as far as the processing speeds are concerned? I know the new ones have built in Ethernet but I am mainly concerned about the processor speeds. I am not able to find a specific processor speed for each processor.

Any help would be greatly appreciated!
Thanks!

The Micrologix1000 User Manual lists instruction execution times toward the back of the book. The other models list the execution times in their respective Instruction Set Reference Manuals.

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1761-um003_-en-p.pdf

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1761-um003_-en-p.pdf

http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1762-rm001_-en-p.pdf

It seems I have seen a chart which compares execution times of the various models all in one document, but don't recall where to find it...it may have been for the Logix platforms...

Paul

Thanks for your reply. I will check the manuals..

Cryogen,


If you are concerned about speeds you may be interested to know that different analog I/O cards can have vastly different A/D conversion times.

We recently had to change out a processor from a MLX1100 to MLX1500 because the Analog input card we could get for the 1100 was too slow. The 1762-IF4 card has a conversion tiem way up around 130ms (I know there is a faster 1762 series card but it is only 12 bits and we needed 15).

So we switched to a MLX1500 w/ a 1769-IF4I and the conversion time is down to 10ms (with 360Hz Filter).It doesn't always make a difference, but when it does, it really does!

In our case, the processor speed was fine but the time it took the analog card to do the A/D conversion killed us.

I guess the moral of the story is you can't just look at processor speed when you are looking at a system. You have to look at everything in the system.

Hope this helps.

I'm also wondering about the reason for concern on processor speed. If speed is essential then there are also things that can be done with program structure that will improve your speed - rarely does everything on a machine require high speed.