Converting Omron C20 to AB MLX1200

[randyy]

I am looking at a dead C20, and the owner wants to go AB, which is my preference too. I have not worked with Omron since trade school. I have taken the paper copy of the program and attempted to covert it to Micrologix1200 using RSL500. The original program used a moderate range of instructions; here is my understanding of their translation:
Omron----------- AB
"KEEP" - - - - - Latch and Unlatch (OTL, OTU)
"TMR" - - - - - Standard Timer
"CNT" - - - - - Standard counter
"DIFU" - - - - - ONS
"DIFD" - - - - - ONF
"IL" and "ILC" - Immediate output w/Mask
also 'apparently' normal I/O (XIC, XIO, OTE)

Admittedly, without a knowledge of how Omron updates I/O, there are parts of the original program that do not make sense, for example:

 

~~~1110~~~~~~|DIFD|

---|\|-------|----|

~~~~~~~~~~~~~|1106|

 

~~~1110~~~~SET

---|\|-------(KEEP)

~~~1106~~RESET |

---||----------| 

BTW, 1110 is also a KEEP coil activated by a system reset PB.
If the DIFD instruction is only valid for one scan, and the reset has priortiy on the KEEP instruction, how can this ever work?
Does the location of the latching coil instruction in the program matter in the Omron controller? Perhaps more importantly, how do you make this work in a MLX1200?

I have the original paper manual for the C20 (Kudos to the owner), but there is not enough information there to make sense of it.

A couple other questions:
- How do the IL and ILC instructions on the C20 compare with the IOM on a MLX?
- What differences are there between the DIFU and ONS instructions?
- What differences are there between the DIFD and ONF instructions?
- Are there fundamental differences between the C20 scan cycle order and the Allen Bradley scan order that affect how you program basic logic? (As I read the C20 scan cycle explanation in the manual, it made me concerned about this point)

As you might have guessed, my first kick at the conversion didn't work. I am trying to sort out the differences between the two controllers to understand why. Many thanks for anything you can do to help!
Randy

:site: is great!

 

[jrwb4gbm]

I dont know Omron but here is how to keep the ladder diagram looking correctly. Click on "Go Advanced" button at the bottom, type in your ladder, "Highlight it", then click on the little button that looks like a relay contact symbol.

 

[randyy]

thanks, jrwb4gbm!

 

[BobB]

Here is a link to the C20 manual.
http://forums.mrplc.com/index.php?app=downloads&showfile=241
It would be a heck of a lot easier typing the program straight into a CP1L. At least you should not have any problems.
The reset is certainly a bit strange. It is quite possible that the print out is not the final, commissioned program and a contact may have been changed at commissioning.
DIFD is a trailing edge one shot.
DIFU is a leading edge one shot.
Have a look in the manual at IL and ILC - they may not operate as you expect.
I think the C20 scans left to right and then down the rung and left to right again. That is a pretty standard scanning routine for PLCs but some are different to others of course.
Have not seen a C20 for a long time - that it has lasted this long is probably a pretty good indication of a good quality build at least. Last one I programmed was in the nineties.

 

[randyy]

Converting Omron C20 to Micrologix

Hello Bob:
Thanks for your post. Having re-read the IL/ILC section, would it be more accurate to compare them with MCR instructions in the MLX? Also, you mentioned that the Omron scans left-to-right then down; when branched output instructions are present between the IL and the ILC instruction, how does that affect the scan order?

Thanks for your help and insight!
Randy