rio flexio, 1794-asb full rack, slot 8 not active

[SoulAnimated]

A controllogix 5550 running a flexio on 1756-dhrio channel b; a remote rack on 1794-asb, loaded I I I 0 0 I I O, where I=1794-IB16, O=1794-OB16; adapter on default, with only baud rate 115k, fault enabled, hold state (dip switches 4,6,7 off on bank sw2).
Adapter configured as full rack.
No error on adapter, scanner, or cpu; online, it shows "InputGroupsValid =2#00000000 01111111. This 0 means no discrete module on slot 8. Question is why?
Replaced module in slot 8, new one still not active.
To me it's the terminal (flexbus connection), couldn't check it yet.
Any clues?

 

[OkiePC]

I have fought through at least ten different problems like yours with Flex IO. Here is what I have found in order of frequency:

1. Check the rev level of the 1794-ASB module and the get the correct instructions for it. AB has changed the functions of some of the dipswitches at least three times in the past few years making it easy for a maintenance tech to create this kind of situation simply by swapping in a replacement module and setting the switches the same as the old one. This is SOP for most techs, and they never realinze that the dipswitches now mean something different to the later or earlier revision ASB.
2. The little toy-like connectors on the flex bus can cause the problem too. I have seen a bent pin cause a problem with a module far from it's location, so when you get the chance to shut down and take it apart, carefully check them all (in that physical rack includig those connected with a flex-bus cable) for bent/broken pins, and be careful putting them back together.
3. With analog modules there are several technotes concerning the timing of power up of the rack with the analog module vs. the CPU. You can find them at AB.com.
4. Bad ASB modules. When 1794-ASB communications (to the processor or to local modules) are intermittent and appear to be electrical noise or cabling, once those are ruled out, replacing the ASB has fixed it for me in 3 different cases.

If I had to make a WAG, I would say you're right on and it's a bent pin. Just wanted to share my experiences with other possible causes.

Good Luck.
Paul