Contrologix Message read of SLC 5/04

yam785 · Jan 11, 2008

I am trying to set up MSG Read in RS5000 to read SLC 5/04 through 1756-DHRIO in slot 5. It seems I have tried everything, but I'm sure I'm missing something. I have steady green lights on CH B on my DHRIO card and SLC 5/04 DH+. Maybe by looking at the pictures below, someone can spot the error of my ways. Any help would be appreciated.

Oakley · Jan 11, 2008

What is the configuration of your SLC_Read tag?

How did you come about using DHRIO as your comm path?

yam785 · Jan 11, 2008

Thanks for response Oakley. This is why I love this site. I prefer not to get answers, just questions that will jog my thinking. As soon as I got your reply, it made me think. Changed SLC_READ tag from 'DINT' to 'SINT' and the problem was resolved. Thanks again.

kamenges · Jan 11, 2008

Originally posted by yam785:

Changed SLC_READ tag from 'DINT' to 'SINT' and the problem was resolved.

I'm confused. Why would that have made a difference, especially considering the error code? Neither data type is native to the 5/04. Even if it was the PCCC request format should have been related to the file type requested (integer in this case). Why would the SLC care about the data type of the ControlLogix container? And if it did care the only data type it should have been happy with is an INT.

Anyone know how this really works?

Keith

curlyandshemp · Jan 11, 2008

kamenges said:
I'm confused. Why would that have made a difference, especially considering the error code? Neither data type is native to the 5/04. Even if it was the PCCC request format should have been related to the file type requested (integer in this case). Why would the SLC care about the data type of the ControlLogix container? And if it did care the only data type it should have been happy with is an INT.

Anyone know how this really works?

Keith

You are right. I have made this mistake many a time. All that happens is byte alignment is messed up, but the DH+ read still occurs without errors

yam785 · Jan 11, 2008

You guys are very sharp, and very correct!

I had all ready been looking into things, and noticed realized I only had 8 bits in my tags. Changed it Tag Type to Int.

It's funny how it allowed me to use Sint, and Dint, but only allowed me to use a certain number of elements for each.

I can't thank everyone on this site enough for the information. I am trying to learn at a 'Ludicrous' pace on this project, and with everyone's help, so far so good.

Thank you!

yam785 · Jan 11, 2008

Yep, I had a beer or two!

Sorry about my wording in last post.

kamenges · Jan 13, 2008

Originally posted by yam785:

It's funny how it allowed me to use Sint, and Dint, but only allowed me to use a certain number of elements for each.

It's all about byte count. The N file type in an SLC is implied as an integer. Your message set-up was requesting a 10 element read, which is 10 integers. This is 20 bytes, which are also 5 DINTs or 20 SINTs. As long as the total byte count was right the instruction would probably be happy.

Keith

CJones · Jan 16, 2008

Don't you have to have two tags? one is the message and one is where you dump it to? (an INT with an array of 10)

Since I've only done this once (last week) I may be way off

Clint

Contrologix Message read of SLC 5/04

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