Indirect Addressing Extremely limited in MicroLogix 1400

[MorphuisOGrady]

Hi,

Am I right in saying that indirect addressing cant not be accessed at file level in these PLCs?

i.e N[x]:1 where x is pointer to address

Thanks

 

[bernie_carlton]

it accepted it here, assuming the target addresses actually exist. While offline, if the indirect value (your x) points to an invalid file you'll get a warning. If, during running, it actually gets to an indirect instruction with the pointer still wrong you'll probably get a fault.

I expanded N7 and added N9, N10 and N11

I entered 9 in N7:5. I entered 10 in N7:6

I entered the instruction MOV N[N7:5].1 N[N7:6].1

It accepted it.

If I changed N7:5 to hold 12 and tried to accept it gave me a warning
"WARNING: File number doesn't point to the correct file type!"

 

[MorphuisOGrady]

OK Bernie, Its just a warning then!. Thanks again

 

[bernie_carlton]

Yeah, I get them a lot. I use indirect cycling through members of files (the last number) using indirect. If I save the values from the running program many times the number is one past the last valid point. it's ok as, before the sequence begins again, I reset the number back to the beginning.

Contrologix used to totally freak out if, during the pre-scan, the indirect would have resulted in an incorrect addressing. I don't think it does that any more.