Bizarre Linx Problem

I was tasked with resolving some latency issues on a DH+ network. There were 16 SLC504's and 4 PV550's on a single segment, all were working properly.

9 of the PLC's (plus 1 PV) are sharing data, so I segmented the DH+ network, creating 2 separate segments. 9 SLC's plus 1 PV on Segment 1 and 7 SLCS's plus 4 PV's on another.

Problem on Segment 1 is that 2 of the 9 SLC's do not show up in RSLinx WHO. Curiously they are working and communicating with the other SLC's on the segment, so it's not an operational issue. These SLCs were showing up previously on the 20 node segment.

No new SLC's have been added, the only change was in the routing of the cables. Cable impedance is within DH+ spec, latency issue has been resolved in MSG communications.

Any ideas?

RSLinx tends to have a memory like an elephant. It gets itself confused sometimes when you move stuff around. This has been more problematic for me with Ethernet devices which have a MAC ID which RSLinx apparently keeps up with internally.

My solution for most of these types of issues is to blow away the harmony files. I do this when I have problems with RSWho not seeing what's really there, and when I have had problems with RSLinx hanging (recent issue for me with Win7).

To do this, shut down RSLinx first. Then search the C: drive for "harmony.*" To save time, you should be able to find them at: Program Files>Rockwell Software>RSCommon.

You should find two files:
harmony.hrc
harmony.rsh
These can be safely deleted. They will be automatically reconstructed when you restart RSLinx.
Let us know if this helps or not.
Paul

Do you have terminating resistors applied properly?