Logix5581/E

[Duane.Edwards 0]

I have created a test program trying to get ready to set up for a machine upgrade and programmed 1 output to check tags.  In the program the output is cycling on and off but the indicator on the output card doesn't cycle on and off.  What am I doing wrong.  I haven't had any formal training and need a little guidance.  

Thanks

[Joe E. 259]

Post a screenshot of your code and your I/O Configuration. Do you have previous experience with other PLCs or is this your first time with any of them?

[Duane.Edwards 0]

I have done programming with a lot of different PLC's.  Physical IO has never been an issue.

[ElectronGuru 81]

Most output cards only have 16 physical outputs, 0 through 15. You've addressed your output tag to 18. Try something at 15 or below.

[Duane.Edwards 0]

24 minutes ago, ElectronGuru said:

Most output cards only have 16 physical outputs, 0 through 15. You've addressed your output tag to 18. Try something at 15 or below.

That was my problem.  Thank you for the advice.  

[Joe E. 259]

Yes, that was it. For some reason, AB uses the 32-bit DINT as a standard data type for at least some IO modules even when they're only 16 points. In your IO config, you show that the module in slot 4 is 1756-OW16I, which is an isolated 16-point relay output module. Your -IA32 modules are 32-point AC input modules and will use bits 16-31.

[ElectronGuru 81]

CLX controllers are 32 bit processors and as such, they like to process 32 bit data. It just works better. Look at this way; if you were moving and everything you owned fit into boxes that were exactly X-by-Y-by-Z, wouldn't that be an easier move than playing Tetris with your furniture in the moving truck? Sure, some of the boxes may not be full but if they're all the same size, it's an easier move. Boxes that are the same size stack and move easier than boxes that are different sizes, even if some boxes are only partially filled. If all your data is the same size (DINT) that's easier to process than different size data packs (SINT, INT, LINT, etc), even if half the DINT data (bits 16 and above) are not used. This is why the default data type in CLX controllers, as well as most IO cards, is DINT. Same size data equals easier and quicker processing of said data in a CLX controller.