Omron 'Ar' register prob


Thread Starter


Have just installed a new PLC (C200hx), and downloaded a program which i wrote previous and is working in identical circumstances in other machines. The problem is when tring to set the PLC clock through AR18 - Ar20. Whatever i write to set the date is instantly overwritten with gibberish. Ie/ i set Ar20 to 0009Hex, which should correspond with month 9, year 00. As soon as this is entered, it gets overwritten with 4020Hex. The register is called and written to when setting the times from the NT631 touchscreen, but only with Ar21.14 on, which is again set from the t/screen. Is this an inherent fault or just a failure of the CPU. I cannot find the reason. Anybody who may know, please respond. Its not the end of the world, just weird.
Hi Mark,

Since you said that this program functions fine in an identical machine, I think you've ruled out programming errors and can assume that there's something wrong with the PLC. But, are the machines indeed identical in ALL aspects? Perhaps the NT screen program is different and may be writing to these registers? Or writing the correct information, but in the wrong format?

I remember (years ago) the first time figuring out how to set the time/date in a C200H took a little "trial-and-error" to get it to work
(mainly getting the hours, etc. into the correct "place" within the word), but in the end was pretty simple. What I did was put the date/time editing control on one screen (on an NT20) and kept the edited time/date in DM. This would allow the operator to abort the editing without actually changing the clock/calendar. When the operator was finished editing, he/she would
"accept" the time/date which would trigger a one-shot (DIFU) that would (all in one rung):

1.) Turn on A2114 (stop the clock)
2.) Move my edited values from DM to A18, 19, & 20
3.) Trigger a trailing one-shot (DIFD).

I used this DIFD on the next rung to turn on A2115 (restart the clock).

I don't see why your method of directly writing to the AR words from the NT would cause any problems. Perhaps A2114 is not staying ON while you write to A18-20?

I hope this helps...I've haven't done much Omron programming lately. Be sure to let us know what you eventually find!

- Eric Nelson
[email protected]
Packaging Associates Automation Inc. [email protected]
Rockaway, NJ, USA