SLC 5/05 Output Image Table Full

Hello All,

I have a SLC 5/05 with 2 13-slot racks of local I/O with lots of analogs and when I went to add another analog output card in the last spare slot it complained that the output image table was full. If I add a remote rack via controlnet (1747-ACN15) or remote I/O (1747-ASB) will I be able to add more I/O? Or is the image table fixed?

"S" stands for "Small(er)"

The SLC-5/02, 5/03, 5/04 and 5/05 controllers have an I/O memory size that is specified in the User Manuals as "4096 I/Os". What they mean is 4096 bits of Input and 4096 bits of Output data.

Background: SLC controller data files have a maximum size of 256 sixteen-bit words. This is true of ordinary B and N data files, as well as the Input and Output data files.

If you are using a lot of analog modules with 4 or 8 or 16 input words per module, you could run out of Input or Output memory before you run out of slots.

The 1747-SN or SCNR will not be a simple solution because they use up to 32 words of Input Table and Output Table memory.

The 1747-SN or SCNR might be a solution for you if you still have N-file memory left in the controller and can accept relatively slow updates from the analog I/O, because you can use Block Transfer mechanisms to get data from the analog modules in the remote rack. You would have to carefully make sure that the number of analog modules did not exceed the available block transfer buffers (generally 32, enough for 16 modules) of the 1747-SN or -SCNR.

If you need analog I/O fast and you're out of I/O memory, then the application is just too big for an SLC-500 controller.

Thanks Ken, the controller in question is the 64k version, so adding more N files should not be a problem. Do I understand correctly that each N file can be up to 256 words?

The problem as I see it (aside from the speed issue and hassle of dealing with BTs) is that the scanner modules take 32 words of non-existant output table memory. Correct?

The scanner can be configured for less than that. It will depend on how many cards you need to access, but I believe you can set the scanner up for the minimum amount. If your existing set-up won't allow you to configure one more card in the local rack, then something else will have to give first...perhaps you can move a couple of cards from local to the remote rack, but I am not sure that you'll gain enough...

Ken will probably be able to give a better answer...can you post the .rss file?

Interesting question about the I/O memory used by a 1747-SN module.

I think that even if you change the "scanned" memory size when you configure the module, that it still reserves 32 Input words and 32 Output words.

I think you'd need to lay out the I/O module numbers and arrangement to get good suggestions on this. Posting the program (or at least the program with the I/O defined) would be a good way.