1747-sn btw/btr 1747-asb

Strugglin_On

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Join Date
Dec 2021
Location
Scotland
Posts
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I have been asked to add new hardware to an old system. The PLC is a 5/04 SLC. In local rack, slot 25, is a 1747-SN connected to a 1747-ASB in a 10-Slot remote rack.
The RIO rack has 2 32-way DI's, 2 16-way DO's and 2 NO4I's. There is a "spare" slot after each of the AI cards.
The 1747-ASB is setup in Discrete mode and 1/2 slot configuration.
Those of you who are familiar with this setup (unlike me) will know that the slots after AI cards are not spare as the Logical Slot is used for the AI address.
I think, from what I can workout from the manual, that I can free up the slots by using Block Transfer.
From reading various post I think I have managed to setup the Block Transfer but like a lot of people I am not exactly sure about the Rack/Slot/Group addressing.
I am hoping that someone can give me a thumbs up or point me in the right direction if I am wrong before I take it to site.

I have setup 2 BTR’s and a BTW for a new 8-way AO that I am adding.
There RIO is setup as below
ASB,
32DI, - Rack 0 Group 0/1
32DI, - Rack 0 Group 2/3
16DO, - Rack 0 Group 4/5
16DO, - Rack 0 Group 6/7
4AI, - Rack 1 Group 0/1
(New 32 DI), - Rack 1 Group 2/3
4AI, - - Rack 1 Group 4/5
(New 8AO), - Rack 1 Group 6/7
(New 16DO) - - Rack 2 Group 0/1

I have setup the transfer block
First BTR Rack 1, Group 0, M1:25.100, Request 4 Words
Second BTR Rack 1, Group 4, M1:25.200, Request 4 Words
BTW Rack 1, Group 6, M1:25.300, Request 8 Words

I have configured the 1747-SN – Full Rack, Full Rack, ¼ Rack.
I will change the DIP switches when I get to site.

I would be grateful if someone could give my settings a once over.
Am I correct in my assumption that the digital cards continue to be treated as Discrete IO when in Block Transfer mode.
Cheers.
 
Welcome to the PLCTalk forum community !

You chose a tricky challenge for your first post.

Your understanding of the 1746-NO4I modules is largely correct. They're part of the oldest generation of SLC-500 analog modules, which use 4 words of I/O data, either all Input, all Output, or split 2+2.

You called the 1746-NO4I an "AI" module, so I want to correct that it is an Output module (-NO4I= Current Output, -NO4V=Voltage Output) so it uses 4 words of Output data, and no words of Input data.

Your understanding of the existing setup is accurate.

In "1/2 Slot" addressing mode, each physical chassis slot is assigned 2 words of Input data and 2 words of Output data. That's why it works with those 32-bit Digital Input modules next to one another. When you need 4 words of input or output data, you need to leave an empty slot to the right of the module you're addressing, which is what was done for the -NO4I modules.

The 10-slot chassis includes Slot 0 for the 1747-ASB adapter, and Slots 1-9 for I/O. In 1/2 Slot mode, you are correct that it's "Two and One-Quarter Racks" of RIO memory.

I think you're also on the right track with configuring the 1747-ASB for "Specialty I/O Mode = Block Transfer" by setting SW3-7 to OFF.

The difference between Discrete and Block Transfer mode is described in the 1747-ASB Adapter module User Manual, in particular on page 3-13 through 3-17.

That will make the 1746-NO4I modules and the new 8-channel Analog Output module only use the low bytes of the first Input and Output word associated with their slot.

It won't affect the discrete I/O modules: they are always mapped discrete and can't use block transfers.

That will leave both of the 2 Input words in physical slot 6 available for the new 32DI module (which will use both) and the 2 Output words in physical slot 9 for the new 16DO module (which will use only one).
 
Hi Ken, thank you for responding. It is from reading your responses to previous posts on this subject that has gotten me to this point.

I am getting my NI4 and NO4's mixed up. They are analogue input cards.

I have seen from previous posts that the addressing of the BTR/BTW blocks seems to cause people the most problems. Do you think I have got the correct group addressing for these.

First BTR Rack 1, Group 0, M1:25.100, Request 4 Words
Second BTR Rack 1, Group 4, M1:25.200, Request 4 Words
BTW Rack 1, Group 6, M1:25.300, Request 8 Words

Paul
 
Thanks for those clarifications.

Yes, I think you have the Rack and Group numbers correct, as well as recognizing the use of the "Module File" data blocks.

Even though the data blocks are 64 words long, they begin at a 100-word offset just so they're easier for us ten-fingered monkeys to understand.

The old manual M1/M0 buffer logic for block transfers is a headache from the 1980's, and if you have a SLC from the last 15 years or so it might support actual BTR and BTW instructions.
 
Hi Ken,
finally made it back to site. The only problem that I ran into was with the image size on the 1747-ASB. After a few stressful hours of frantic internet searches I found that it was a DIP switch setting. Switch 2 DIP's 5 - 8 were set for 15 words, which took me up to rack slot 8. This prevented my DO card from working. Changed the DIP switches to match image size in the 1746-ASB and the rack size in the 1747-SN.
Thanks for your help.

Paul
 

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