AB PLC5 Addressing Question/Issue

Hello I have an Allen Bradley PLC 5 system that had been updated from a PLC 3. I have a question about indirect addressing that I cannot get my hands around, I have a mov function with an source address of B[155]:[0]. This address confuses me as it does not seem to refer to a file in my system. When I right click on the address and select find all or go to data table it directs me to an address of B[N180:7][N181:7] this address I understand. However I cannot figure out how B[155]:[0] = B[N180:7][N181:7]. I can provide screen shot if that would help.

Thanks

welcome to the forum ...

I'm not 100% sure I understand your problem - maybe a screen shot WOULD help ...

or take a look at the following post ...

http://www.plctalk.net/qanda/showthread.php?p=91682#post91682

maybe it's just the way your display is set up that's confusing you??????????

try a RIGHT-CLICK on the ladder display window and choose PROPERTIES from the menu ... then go to the Address Display tab and change the setting shown ...

Going from memory

It has been awhile for me with a PLC5, but I'm wondering if B155:0 does not exist, and is either an error in the conversion process, or a typo. Are you experiencing a problem with this? Is the rung even accepted? If the answer to the latter question is no, then it might be that the data table is simply displaying the first valid address after the one you requested. Again, this is from memory, and I can't verify that it will do that. One way to tell is to look at the cross reference for B155, and see if you are allowed to select an instance of usage of B155, and if so, if it takes you to where the B187 is used. Of course, all of this is speculation, and if the rung compiled, then none of this makes sense.

Russ

And if Ron's link is not the answer ( I bet it is) then post your .RSP file (zip it first). Screen shots usually don't help much.

It is simply an option in the software to show the values of an indirect address, instead of the address itself.

Most times you want to know what the indirect is addressing, (i.e. where the data is stored), not how the address is formed.

You can switch back and forth to show the indirection, or the location of the data.