SLC I/O as RIO on Control Logix

[bof 1]

One plant I work for standardised on SLC I/O. This started as a cheaper alternative to PLC5 I/O but the plant now has SLC I/O hanging off PLC5, SLC, and Control Logix processors - all using RIO. What we have noticed is that the Control Logix (1756-DHRIO Scanner) with SLC I/O combinations are prone to faulting with comms errors. Sometimes once a week, sometimes several times a day. Sometimes they go for months without problems! Now I know everyone will shout 'electrical noise' as have AB. Our problem is that we have been through all the recommended installation details without any noticeable change in the error rate. Also we have the same SLC I/O on RIO hanging off PLC5 and SLC in the same environment without any problems. Anyone else experienced anything like this? Any thoughts?

[JeffKiper 9]

Once apon a time about two jobs ago we had a DH+ / RIO card in a bridge that was acting up ever once now and then. We changed the card and the problem went away. We later found that the card was an older REV. We had bought 3 card 2 where new 1 was old.

[rpraveenkum 5]

Older firmware have lots of communication issues better to upgrade the cards to latest firmware

[Ken Roach 194]

I wish folks would post more information and fewer guesses. It's been a long week. Post more information about the errors that you're encountering on the 1756-DHRIO and 1747-ASB links. How many devices, what sort of cable lengths, what kind of errors and how they are reset. Each 1756-DHRIO has some channel-by-channel diagnostics about bad packets and retries. Have you used those to characterise your steady-state system conditions ? Lets be clear about revisions, too. 1756-DHRIO has had four hardware editions (Series A, B, C, D) and several firmware releases for each.