Question about the "requested word count" item in BTR/BTW

Hi. I'm new to this board, but hope someone here may be able to help me out. I have a question about the "requested word count" item in a block transfer instruction.

I actually am going to be using a 1747-SN connected to a rack with a 1747-ASB and four analog input and output cards (NI4 in slot 1, NO4I in slots 2 and 3, and an NT4 in slot 10). The other slots will have IA16 and OA16 cards and will map discretely. I plan on using 1-slot addressing. If I start at Rack 0, Group 0 (and if I understand this correctly) then I'll be using slot 0 in Group 0 for the NI4, slot 0 in Group 1 for one NO4I, slot 0 in Group 2 for the other NO4I, and slot 0 in Rack 1, Group 1 for the NT4 (the other input and output cards fill the intermediate groups).

My question is this...do I have to have individual block transfer instructions for eack group? My first thought is "yes" because I have to specify rack, group, and slot in the BTR/BTW instructions. If this is the case, then I'm assuming my "requested word count" for each BTR/BTW instruction would be 4, since these analog cards have four words.

However, in the manuals I see that you can request up to 64 words. How can you do this? Is it possible for me to use one BTR or BTW instruction for the whole logical rack 0? Would I use a requested word count of 8 for the NO4I in the BTW instruction? If this is the case, then would I have to use two block transfer instructions because I'm crossing into rack 1?

Most of the examples I'm finding show you what to do if you have one analog input card or output card in your ASB rack. I really need an example showing two or more.

Thanks

There are some things about your setup that I'm not sure I (or perhaps you) understand. They mostly involve your rack/slot/group addressing (which are dependant on the DIP switch settings on your ASB module for single-slot addressing, complimentary addressing, etc. If you need any help on that, just post again.

What you'll do is set up one BTW/BTR for EACH module that you will be communicating with.

Each BTW/BTR pair will have the rack/slot/group of the logical rack/slot/group of the device (again, depending on the type of I/O addressing the DIP switches on the ASB specify).

In the BTR and BTW instructions, you will have a "Buffer File" of M0:x.y00 or M1:x.y00 (the BTW will use M0, the BTR M1), where x is the slot number of your SN module, and y is a unique number for each transfer. That is, if you use M1:1.100 to read your NI4, you can't use M0.1.100 to write to your NO4I, but could use M0.1.200.

As for your question, "requested word count", you'll need to look in the NI4 and NO4I manuals, but I think that you would only need 5 words, 4 data and one status (but I could be wrong - the manual should tell you.)

That should be enough to get you started.

Thanks for the reply, Allen. I see where my description may have gotten a little confusing. I should have stated the "ASB rack" as ASB chassis. And my other references to Rack, Group, and Slot were in reference to the logical rack, group, and slot designations on the input/output image table worksheets from the 1747-SN manual.

I see what you are saying about using different "y" values from each module. I think this answers one of my questions. I will have to have an M file for my NI4 module, and then separate M files from y other NO4I and NT4 modules.

I did find an example program in the AB knowledge bases that says it shows block transfers for a chassis with an NO4I and NT4. I haven't opened it yet, but I'm hoping this shows me a multiple module/multiple block transfer setup.

Brillohead said:

....I plan on using 1-slot addressing.
If I start at Rack 0, Group 0 ... then I'll be using
slot 0 in Group 0 for the NI4,
slot 0 in Group 1 for one NO4I,
slot 0 in Group 2 for the other NO4I, and
slot 0 in Rack 1, Group 1 for the NT4
(the other input and output cards fill the intermediate groups).

Click to expand...

Now that work is done, and it's Friday, I've got a few minutes to really look at your first post.

I'm pretty sure that you have it wrong. With 1-slot addressing, the physical slots are the same as the logical slots, and the group number is always zero.
So your NI4 would be in slot 0, group 0,
the first NO4I would be slot 1, group 0,
the second NO4I is slot 2, group 0,
and the NT4 would be slot 3, group 0.

That may help.