DH485 network slowed down.

[SDM 0]

Hello, I have a old DH485 network it had 3 PV 550's, 2 SLC 503's and micro on it. I removed 1 of the PV 550's and 1 SLC that I up graded to an Ethernet network. My problem is after I removed the 2 Nodes from the 485 network, that network went very slow. e.g We have some DMX card in the system the operator can jog the cylinders by pushing PV button. This loads the furthest distance into the DMX cards. If the button is released a 0 is loaded into the cards. It use to be if you pushed the button it started moving and stopped moving as soon as you released the button. Now even if you just bump the button the cylinders move a foot or more before stopping. Like the processor sees a delayed release of the button. Also there is an encoder on this system there are LIM's for different areas along the travel. Since the change the system started blowing by the limits so I added a latch to the coil the limit triggers. Yesterday the system stopped and when I hooked up to it the encoder reading was beyond the limit and the latch had not been made. Like the Logic never saw the encoder reading with the limit? This is an existing network from before I came here and previously I have always used Ethernet, DeviceNet, or Profibus. I would love any help you all could give me. Thanks

[Ken Roach 194]

DH-485 is a "token passing" network that supports up to 31 nodes, and the sequence of node numbers can be important. A typical optimized DH485 network has node numbers starting at and incrementing without gaps. 1,2,3,4,5,6,7. Most devices also have a setting named "Maximum Node"; this sets the maximum node number to which the highest-numbered device on the network will attempt to pass the token. For a fast network, set this to the highest node number present. Often one higher node number is included for occasional connection of a PC, but Node 0 can also fill this role (I think... I always used the superstition of having an empty high node). There's another setting called Token Hold Factor, which can be from 1 to 4, default 2. This determines how many transactions a node can perform before passing the token. Higher values allow the node on which it's set to do more (like a PanelView that needs to read a lot of data), while a value of 1 allows the token to pass faster to other nodes. While DH-485 is fairly noise resistant, being based on RS-485, it's not impossible for noise to be a problem on your network. See if any of the Channel Diagnostic "Messages Retried" or "Bad Packets" counters are incrementing on your controllers.

[slcman 9]

I'm agree with Ken reply. Just want to add one point, be sure other plc doesn't try to msg the SLC you removed from DH485 network. Communication timed-out is a common cause of comm problem.

[SDM 0]

Thanks, I will start with Ken's comments I know that there are gaps in the node addresses also all the maximums are set to 31. 1 plc has the token set to 1 and the other is set to 2. I can't see where to set the token hold factor in the PV though.

[Ken Roach 194]

Good point; PanelViews don't have an adjustable token hold factor. If your system worked correctly previously, and there have only been devices removed from the network, then it can almost certainly be restored to at least its previous level of performance.