QUOTE(JAK @ Apr 11 2008, 03:40 PM) [snapback]67659[/snapback]
I have a SALESMAN telling me that the Camera system that he has will talk to an AB plc over Ethernet IP. I am going to talk to a PLC 5. I understand that the PLC,SLC and MLX family processors talk over AB Ethernet IP. SO I figure that I am going to need a converter. I would like to have a converter in the cabinet with the PLC 5. I am trying to keep away from the CLX bridge idea. Can anybody suggest an alternative?
AB has several different protocols. PCCC and CSP are roughly speaking, based on a slightly modified version of DF-1. Ethernet/IP uses CIP format (among other things) and is nowhere near a direct translation from DF-1. The PLC-5 uses PCCC. SLC's use CSP (and Micrologix to some extent), and CLX uses CIP. HOWEVER, you can also get all of these processors to intercommunicate with each other in various formats. The latest version of the PLC-5 (have to do a firmware upgrade, which is free), can also talk CIP.
You can use unsolicited MSG'ing (MSG blocks) almost interchangeably between processors. If you run into trouble Prosoft Technologies makes a converter. Digi One IAP also does an excellent job (at a much better price) of converting between PCCC, CSP, and CIP.
That being said, this is talking about EXPLICIT messages (to use AB's lingo). It is not referring to unsolicited messages. Although there is such an animal with CSP, CIP takes it to an entirely different level. If you are trying to do Ethernet/IP-based I/O, and not passing information via MSG blocks, then as far as I know, you can forget about doing it with a PLC-5. At least I've never yet figured out a way to do it. Ethernet/IP based I/O uses multicasted UDP packets where all of the other protocols I mentioned are based on TCP. I don't know of any protocol translators on the market that make this leap.
AND, using a CLX backplane as a protocol translator will NOT work if you are dealing with unsolicited messages. In other words, you simply can't use CLX-based I/O from a PLC-5.
As to the camera manufacturer's knowledge...AB protocols are weakly documented. AB has flat out refused to document anything about Universal Remote I/O without paying a 5 digit figure as a supplier. Ethernet/IP is hidden behind the ODVA pay-to-play firewall. PCCC is essentially completely undocumented anywhere and the documentation that is available is wrong. And I have never turned up anything on DH485 either. At this point there are no less than 4 protocols in reality just for Ethernet (Micrologix also has a slight variation on the theme bringing the total from 3 to 4). You need to find someone within that company who knows exactly what they are talking about and knows the ins and outs of AB communication protocols, or you will never get anything to work.
I do have a possible answer though. Use Modbus (either Modbus/TCP or Modbus/RTU). Why? Because it's the lingua franca (universal language) of PLC's. You can either use Modbus natively or get a protocol translator for EVERY PLC ever made as far as I can tell. Strangely enough, most members of the Micrologix family will NOT support any of AB's own remote I/O protocols but they do support Modbus just fine. Any time that I use Modbus for tricky protocol problems, I find all my problems melt away.