Why use a COP #M input source to #B9?

[plaurent]

Trying to understand a program someone else wrote.

What is the reasoning behind a COP instruction for source #M for an input to a #B9 binary tag? Why wouldn't the original author simply specify the Input tag in the ladder?

 

[OkiePC]

M1 and M0 files are required for some smart cards in a SLC. Accessing those files takes considerable scan time. It is better to do it once with a big COPy rather than have a bunch of references in the program, since they're physically located in the smart card. If you can post the code we can probably tell you a lot more (zip it first).

 

[plaurent]

Thanks for taking a look...

 

[OkiePC]

Yep, you have a devicenet scanner in slot 1. The scanner can give you 32 words in and 32 words out, but if you need more, you have to use M0/M1 files.

Each time the SLC runs across a reference to M0 or M1 data, it must send information to the smart card and wait for a response, so it's better to do it once with a COP rather than dozens of times with OTE or XIC instructions. Also, the status of the M0 and M1 files cannot be monitored directly in RSLogix500 so you need a copy anyway to be able to see what's really out there.

 

[plaurent]

Many thanks. Devicenet is a new beast for me... obviously.