Network Lockup problems

Hey everyone,

I'm still working out issues with the 6 1500's and a pv600 on a dh485 network. As I have described in the past, when operator presses a PV button,I am using PLC1 to write a MSG of 1 word out to the other 5 PLC's.They each look for that word to change and then initiate a READ of 206 words(broken into 2, 103 word MSG's) from PLC1.The system is already installed and my customer says that it quits working and data does not get moved to the other 5 PLC's.He also says that he can power down the PLC's and then turn them right back on, Press the button again and everything Works OK. My question is, What does powering down the PLC's do to fix the network problem and what can I do to permanately fix it? I don't think that the PLC nodes drop off because the PV still displays data from them.Is it because all 5 PLC's are trying to read the same data from PLC1? I thought that the communications buffer and queue handled that. Any helpful thoughts would be appreciated..

I'm not sure this will help, but if you are using the AIC+ module there is an issue with the "standard" Panelview cable connected to the AIC+. The power connections on the two DB-9 connectors are tied together and this pulls down the network.

We hit this on a project last year. We replaced the A-B cables with our own that only had 2 3 and 5 connected and life was good again.

Tom,

We have a 1761CBLPM02 and a null modem adapter as the cable going from our PV to the AIC+.
Do you think this is our problem?

It's possible. I think we used a straight through cable built 2-2 3-3 5-5 DB9 to DB9