INDEXED ADRESSING HELP

[wonderboutin 0]

I have a 15 "MSG" instruction on my 5/03. I try to replace my 15 "MSG" for 1 "MSG" with indexed adressing but I have a compiled error "Indirect adress not allowed!" In setup screen of my MSG, Data Table Address = N[N10:3]:0 I try with N51:[n10:0] and I have a error. Help me please!

[Guest]

before you attempt this project, let me ask you a quick question ... why? ... please consider how incredibly complex it will be to troubleshoot any one of the message transactions in the future ... instead of having one nice simple independent MSG rung to work on, the technician will be forced to try isolating just one set of parameters out of a lengthy series of parameters ... and the series of parameters will be constantly changing from one MSG operation to another ... in most cases, the only way to identify/isolate/troubleshoot the "problem" transaction is to "stop the show" on all of the other MSG transactions ... in most cases, that is NOT a good idea from either a production or a safety standpoint ... I've seen things like this done before ... it is NOT something that I'd recommend ... my advice is to keep things simple ... use a separate MSG command for each separate transaction ... future technicians will thank you ... otherwise, they will curse your name ... Edited 8 Nov 2006 by Ron Beaufort

[TimWilborne 108]

I second Ron's recommendation. I did this one time because I was on a smaller is better kick. It worked great until we had some communications problems. Troubleshooting was a pain for a small reduction in memory

[autocontrolit 0]

If I'm not mistaken you need at least a 1747-L54* Series C to for the processor to handle indirect addressing. I am not sure a 5/03 will handle indirect at all. I still must ask the same question though why? The only time I have used indirect is for scanning purposes, and that was only once to scan 2 seperate datafiles with 100 msg instructions each, and then I resorted to this only because I had to add the edits into multiple processors after corporate IT "upgraded" our ethernet causing major messaging errors. I was able to scan 200 MSG instructions for errors and reset them with 1 rung of logic, but this is an extreme example, and was necessary until our "upgrade" received an upgrade.

[BobLfoot 302]

I'll jump on this wagon with my 20+ years experience. Any time I see indirect addressing used ad nauseum it often means the designer was too lazy to type all the code to do it plainly. Stick with the simple message instructions.

[Ken Moore 23]

I must agree, DON'T DO IT

[BobLfoot 302]

if you go against the chorus this post might help.

[Peter Nachtwey 15]

So how many MSG blocks must there be before one consders using indirect addressing? Indirect or index addressing is a tool. It is neither good or bad. It all depends on how the tool is used. BTW, I would use indirected addressing to copy the data to a buffer. The msg block always read or writes using this buffer. There are some gotchas. The buffer should not be accessed while the MSG block is enabled and not done. I just look at the .DN bit.