[debug mode - checking logic]

Thanks that was helpful.

Sadly my program won't download due to system error '9'. I've emailed the code to unitronics' support team so hopefully they can help me with it.

Another question though while we're here:

In the code I uploaded I found output set and reset coils connected in series. I understand this will work for Memory BIts, but can you do that for output coils? Surely they should be connected in parallel.

Cheers

[debug mode - checking logic]

I'm a new user of Ladder Logic and M91 PLC's. I'm trying to debug a program I have uploaded off of an old PLC.

I understand that in U90 there is no way to force input/output states. Considering this how can you check that your logic is correct?

E.g. how can I check that a certain combination of inputs will cause a change of state or particular output?

[i don't consider a red flow of logic sufficient, especially as I can only see it for the power on state.]

Thanks