In essence CSMA is always active checking if someone is holding the line and if not it will send and at the same time use Colition Detect just in case someone sent in the exact same time. Collition Detect sense if there is a collision and waits a random time before retransmittion, and Carrier Sense Multiple Access is a detection method used to avoid collisions by sensing if someone else is sending data in the first place. CD/CSMA is "Collition Detect / Carrier Sense Multiple Access" which occurs when you have several devices sending data at the exactly same time on the same wire. Have you tried to confront Westermo with the CD/CSMA answer? I think they might have misunderstood something since this is a feature of Ethernet star network. Are you sure that collisions are causing the problems, and not other errors?Ī couple of screenshots would be nice indeed, as much info as possible. As long as you use a polled protocol (which you do), only one request is sent at any given time, and since all PLCs have unique addressing, only one response will be sent for each request. Again, I find it very strange that there should be collisions. 1000ms)? Maybe the response doesn't have the time to return before a new request is sent, hence you will have collisions. Have you tried to rise the timeout (from 500ms to e.g.
Kepware tech support serial#
Do you have some dump files from the serial monitor? It would be interesting to see "where" the collision occurs, and which device is actually sending data where it should not? 3. Is it possible for the Kepware server to send only to one segment at a time so that there will never be more than one PLC responding at any given time? Just as a test? 2. Do you have a dump from the monitor where the actual collition occurs? 1. I don't understand why Westermo responded to you with the CD/CSMA which is a Ethernet star network technology, and the TD-29 uses 2-wire bus setup which, as long as the Kepware does it's job correctly, will not have collisions on the two-wire interface. The strange thing here is that there shouldn't be any data collision on the TD-29's. Could the serial/ip converter be failing, or be wrongly configured? I would guess that the serial/ip converter also has a timeout, or is it a straight-through device? Maybe you have some more information/specifications on it? Do you have unique addressing on absolutely all the PLC's no matter which segment, or do you have several similar addresses distributed on the different segments? Could it be that the ip/serial converter sends the request to all the segments, so that you will have a collision when two PLC's respond to the same message? 3. Does the Kepware server send to multiple segments at the same time, or does it go through it's list of PLC's, communicating with only one PLC at a time no matter which segment it's on? 2. Also you have three serial outputs from the serial/ip converter, I'll just call them for segments so you basically have three segments connected to one serial/ip converter which is then connected to the server. Are you sure that the serial/ip converter isn't failing? If the Kepware server doesn't send multiple requests at the same time then there should be absolutely no collisions on the network/bus.