Darn these A-B RIO

[Williyb]

Ive just started learning about RIO lately, I have no expierence with them. I do have a basic undestanding how it works,but my question is "If I have 5 remote racks in the plant and I want to add one more, do I have to add it to the end of the cable or can I add it in the middle. I'm asumming I cant address it as though it was the last rack on the network." I did just that and cant get the 1747-asb to communicate, it goes thru the set-up and then shows no-com? I dont want to have to change the adressing of the next two racks, but it starting to look that way. Bear with me i'm trying to work thru this, I think I have the BTR,BTW figured out but I know I'm missing something.

 

[PhilipW]

Hi...yes Remote I/O is a system with a long history, and as a result is a bit hairy chested the first time you come accross it.

Couple of pointers:

1. A "Rack" is defined as "8 Words of Input and 8 Words of Output data table image in the PLC scanner". A "Chassis" is something you can bolt to a wall. A Scanner is the Master in the network, and all other slave nodes are Adaptors.

2. Remote I/O is always cabled as a trunkline system. NO star points (more than one dropper at a single location) are permitted. Always use a terminating resistor at each physical end of the trunkline.

3. Any node can be placed in physical order on the trunk. Adding a new adaptor can be done anywhere on the trunk (so long as the physical wiring rules are followed) and it can have the any spare Rack Address free within the PLC scanner.

4. One really common mistake is to reverse the polarity of the Blue/Clear wires in the R.I/O cable. If these wires are crossed anywhere in the network, then it will NOT work.

5. Also remember that you have to match up the Baud rate to be the same at all nodes.

5. I think you should be able to add the new adaptor without changing the old rack addresses..but I don't have enough details to help.

 

[Allen Nelson]

Other things to consider

Since you mention 1747-ASB, I'm guessing that your processor is a SLC. Have you modified the 'G' table so that the -SN module "knows" about the existence of the new chassis?


The order that the racks are wired in does not have any relation to the order on the RIO line. The scanner can even be located in the middle of the string, the key is that the modules are daisy-chained, not starred. When you added the new rack to the middle, did you cut the existing blue hose and add it in (alternatively, did you remove one set of blue hose wires from an existing node, wire those to the new ASB, and then add a new blue hose between the two, as below:

     _____

     |OLD|

     |ASB|

      /\

     /  \

____/    \_____________



     _____        _____ 

     |OLD|        |NEW|             

     |ASB|        |ASB|

      /\__________/\

     /   ___________\ 

____/    \___________________

Phillip's advise about double-checking the polarity on the blue hose is worth repeating - it is the most common mistake.

To expand on Phillip's first point, does the new ASB "rack" overlap any other chassis' "rack"? Some chassis can be more than one "rack" (8 x 16-bit words) long. The 'G' files in the -SN module configuration may give you a hint about this.

 

[john paley]

What kind of equipment is in the scanner rack?? SLC 1747-SN??? If so, you only get four logical racks--period--0,1,2,3--32 I: and 32 O: words addressed to the slot where the SN module resides. You can, however, split these logical racks into more chassis with fewer than 8 slots. Say two chassis assigned to rack 0--one words 0 thru 7, one words 8 thru 15. (Use rack size, 1/4, 1/2, 3/4, full, and starting quarter to do "split" a logical rack to two chassis)

If the scanner rack houses a PLC 5, check it's RIO limitations--some of the smaller 5's only give a little RIO--some 5's give a lot.

My point is that maybe you've addressed a rack too far.(high)

 

[Williyb]

Thanks for the advise I'm starting to pick it up from this site and the AB manual. Allen, right after I sent the thread I search for more info on RIO and came up with the post that talked about setting up the G files. Found it, added it, It was like a light bulb turning on. For some reason I couldnt figure out how the SLC knew it was there. I did split the cable and add the new rack then ran a new cable to the next rack. If I undestand from everyones replys is that, Lets say I have a e-stop to add to the line is there are already 5 with 5 differant inputs. I:1/32, I:1/64 I: 1/96 I:1/128 I:1/160. I want to add I:1/192. Since I:1/192 is physically in between I:1/96 and I:1/128 (since that's where I split the blue hose) If what your saying is it doesnt matter where the rack is on the line than I can address it this way?

 

[Kim Gold]

Here is a screen shot of the G file. You can address your rack wherever you have space.

Also here is a link to the manual for the 1747-SN scanner module, which may be of some help.

Remote I/O Scanner 1747-SN