AB SLC Analog Card Initialization

pablo2000

Member
Join Date
Aug 2004
Posts
29
Hello,
I've inherited a program controlling a hot water skid and I've had to replace an analog input card (1746-NI8) at slot 5 in the rack. When I enable and configure the card through the channel configuration dialog and accept it, a rung is automatically entered at the top of File 2 copying 8 words from the N7 file to Outputs O:5.0 to O:5.7. I have never seen this happen before, although I presume it's standard stuff. The value in the N7 data words is 3853 (decimal). Can anyone explain what's happening here? Why is it writing to outputs at slot 5, when that is an input card?

Pablo2000
 
When you configure the IO for the SLC500, memory words are allocated in the IO image file for the card. Usually I and O words will correspond to a physical input or output so we sometimes start to think that the card works that way. But as far as the PLC is concerned I words are used just to read data from the card and O words are used to write data to the card. The card determines what to do with the data. In the case of your analog card the O data tells the card what format to return the analog data in. I usually define a dedicated N file (usually N18 in most of my programs) which contains the static configuration data for the analog cards.

You can find more information about this in the AB literature library. Go to http://literature.rockwellautomation.com/idc/groups/public/documents/webassets/browse_category.hcst and enter the catalog number of any module you need information about into the search field to find all of the manuals on that card.
 
Last edited:

Similar Topics

Hey guys, Well, the troubleshooting continues for the client who got hit by lightning. New CPU has been installed, and is working! That's the...
Replies
12
Views
3,292
I'm working with an AB slick 500. It's running a RO system for the boiler room. I'm trying to interface with a transar system so they can monitor...
Replies
5
Views
2,711
I'm feeling pretty stupid tonight because I can't remember process to install and set up my 1746-NI4 analog card in my SLC 500 PLC. It has been...
Replies
2
Views
3,855
Can I change the analog module (8 channel analog) configuration i.e. write bits to the configuration file while online with the PLC? Do I have to...
Replies
10
Views
5,913
Calibration What i am trying to say is: If i put a rtd in my dry well temp calibrator and it is set for 86C then I...
Replies
5
Views
2,645
Back
Top Bottom