Enable Analog Channel in RSLogix 500 // First Scan Bit, COP function?

[James275 0]

Hello all.

I have been working with an SLC 5/04 system, which houses various Digital and Analog INs and OUTs, up to Slot 29. I am currently mainly working with Slot 25, an Analog Input: 1746-NI16I. This is a system which has already been set up and has been running for the best part of 8-10 years. This particular card has had some spare inputs, one of which I am trying to connect to. In the Advanced Configuration, only a few Channels are actually "Enabled", and each channel is pretty much slightly different from another in terms of Input Type, Filter Frequency and Data Format. I am trying to set up Input 14, which is Channel 15, to "Enable" it, 4-20mA Input Type, Filter Frequency of 6 Hz and Data Format of either Raw/Proportional or Engineering Units.

Now, after I have made my choices, I click apply, and then OK. I am then confronted by a pop-up which states:

"Configuration Rung and Data

Integer Data File Number: 25

Integer Data Element: 100

Rung to be inserted: XIC S2:1/15 COP #N25:100 #O0:25.0 24

At Program File Number: 4 82"

I have the options of OK or Cancel. If I click OK, I now have LAD 4, Rung 82 Highlighted. This First Scan Bit and COP function were already here, but does that mean I have now altered what is being written to "#O:25.0"? I now Download the Changes. However, after all this, I am not getting any Analog input reading coming in from the Live PLC.

What is this COP function? What does it do? How do I properly set up this Analog Card?

 

Thanks for your time,

-Jame

[panic mode 246]

COP instruction copies one more elements from one location to another. Equivalent in this case would be using four MOV instructions. This is well documented.

[James275 0]

Hello Panic Mode. Thanks for the response, but what I meant was, in this case, What is the COP function doing in relation to Enabling an Analog Channel or changing items in the Advanced Config? Why does it need to create the new Rung with the First Scan Bit and the COP function point to the "#O:25.0"?

[Joe E. 259]

In these processors, some of the module configuration (especially analogs) is handled by writing values to the output image table. That's what the COP instruction is doing. It's writing to the module configuration registers on the PLC's first scan.

[Shiner 2]

To expand on Joe E's comment, during power up, any values that were written to the AO previously will be written over by the values held in the 4 registers referenced by the copy instruction.  If those are still at default 0, then your output will start at 0, as that is the assumed safe state.  If an alternate safe state is required at startup, those values should be manipulated appropriately.  If those values are being used by something already in the program somewhere, you may be writing in undesired values at power up.

[James275 0]

When trying to Enable new Channels, I am encountering the popup with: " Rung to be inserted: XIC S2:1/15 COP #N25:100 #O0:25.0 24 ". Now, before I click OK, the Rung is already there (82), with the COP function Length of 4. When I click OK, the COP Length does not change from 4 to 24. Do I need to manually alter this to 24?