Mystery Bit?

[Dave_BP 0]

I'm a newby here so pardon my dumb question please. Here goes............... In a PLC 5/12 Series A processor there is an input bit (I:031/1, labeled "PLC 5/40 Communications Status Bit") that is giving us intermittent alarms. I have cross referenced the point, looked by hand through the IO Configuration tables, etc. and it only shows up in one rung, driving a XIC contact. Can someone tell me what else I can do to find the ultimate source of this bit? It looks like something is writing directly to that location. There may another PLC 5 talking peer-to-peer with this one, but I can't say for sure as there is no Channel Configuration information available for the 5/12 in RSLogix for some reason. Any ideas? Thanks for a geat forum. Dave Standerfer BP Alaska

[Leadcommander 0]

Hello Dave Since you say you are working with a PLC5/12 but the message associated with the XIC is "PLC 5/40 Communications Status Bit", my guess is that the PLC 5/12 is using RIO to talk to a PLC5/40 in Adaptor mode. This means the PLC 5/40 will operate with its own code but has one of it's communication channels set to adaptor mode. Through this adaptor mode you will get what looks like real Input and Outputs in the 5/12. These are internally mapped in the PLC 5/40. The other possability is it is a physical input on Rack 3 module 1 input 1. Cheers

[Dave_BP 0]

Thanks for the feedback. On the 5/12 there is no Rack 3, only a Rack 0 with 4 1771-IBD's. How can I tell if it's using RIO? The 5/40 channels are setup as: ch. 0 = ASCII, ch. 1A = DH+, ch. 1B = DH+, ch. 2A = Remote I/O Scanner, ch. 2B = Remote I/O Scanner, ch. 3A = Ethernet/C. Are any of these what you are refering to? Thanks again. Dave

[Mickey 71]

If you can post your .RSP file for both the PLC5/12 and the PLC5/40 maybe someone can spot something. Is there anything connected to the DH+ port on your PLC5/12. Is there anything connected to yor RIO port on the PLC5/12. There could be comms across the DH+ ports with messages going back and forth or one way. There could be comms using global status flags across the DH+ port. As you can see lots of things are possible here, no way to tell without more info. Again .RSP files would help.

[Guest]

Greetings Dave ... and welcome to the forum ... you haven’t given us enough information to really nail this down ... but I’d bet more than pocket change (but less than the rent) that your PLC-5/12 is operating in “the Adapter Mode” and that the PLC-5/40 is operating in the “Scanner Mode” ... here’s the basic idea ... the PLC-5/12 has its own local I/O and runs its own program ... no surprises yet ... but ... part of the PLC-5/12 also functions as a “Remote I/O” device ... so ... PART (but not all) of the PLC-5/12’s OUTput table is “mapped” into the PLC-5/40’s INput table ... and ... PART (but not all) of the PLC-5/40’s OUTput table is “mapped” into the PLC-5/12’s INput table ... specifically, when the PLC-5/12 turns on one of the “shared” OUTput bits, the corresponding INput bit in the PLC-5/40 also turns on ... survival tip: in BASIC terms it doesn’t hurt to think of the PLC-5/40 as being a “Remote I/O” device of the PLC-5/12 ... specifically, the PLC-5/12 is actually “controlling” the status of some of the INput bits inside the PLC-5/40 ... and going further ... the PLC-5/40 has its own local I/O and runs its own program ... again, no surprises ... but ... part of the PLC-5/40 also functions as a “Remote I/O” device ... so ... PART (but not all) of the PLC-5/40’s OUTput table is “mapped” into the PLC-5/12’s INput table ... specifically, when the PLC-5/40 turns on one of the “shared” OUTput bits, the corresponding INput bit in the PLC-5/12 also turns on ... survival tip: in BASIC terms it doesn’t hurt to think of the PLC-5/12 as being a “Remote I/O” device of the PLC-5/40 ... specifically, the PLC-5/40 is actually “controlling” the status of some of the INput bits inside the PLC-5/12 ... here’s a “main idea” sketch that might help ... the “main idea” is that SOME of each processor’s I/O bits (the highlighted sections) are “SHARED” with the other processor ... you can find more about this “Adapter Mode” set up for the PLC-5/12 in this manual if I’m on the right track, the information in Appendix A should be very useful ... hope this helps ... if not, please post more details about how the DIP switches are set up in your system ... we’ll be glad to try again ... and as my distinguished colleague Mickey says, the .RSS files would REALLY be helpful - if you're allowed to post them ... Edited 14 Mar 2007 by Ron Beaufort

[Dave_BP 0]

S_Pad_PLC_5_Files.zip Ok, here are my .RSS files: S441_F&G is the 5/12 and WPS-MAIN is the 5/40. Thanks for all the help. I've already learned a lot! Dave

[Guest]

see if this helps ... if you need more detail, then we'll need the DIP switch settings from the PLC-5/12 ... the figure below is the TO part of the picture ... the figure below is the FROM part of the picture ... and the figure below should give you an overview of how four words of input bits and four words of output bits (one half rack) are being transferred between the two processors over Remote I/O ... note that you can click on the figure to enlarge it ... hope this helps ... Edited 13 Mar 2007 by Ron Beaufort

[BobLfoot 302]

As usual an excellent job and photo's Ron. One observation, not all your bits are in sync.

[Guest]

I noticed that too ... my guess is that there was some amount of time between when Dave saved the two programs that he posted ... that's the easiest (and most logical) way to account for the differences ... and thank you for the kind compliments ...

[Ken Moore 23]

Another mystery solved. Good job Ron.

[Dave_BP 0]

I just got back from a week off and all I can say is WOW! Thanks so much for making that all so clear. The files that I sent were backups from different dates hence the bits look to be out of sync. Thanks again.