R
Roger Irwin
> If that is true, then you can give up on any solution based on Modbus. I don't see the EDP/IT world moving to Modbus.
Well I can access a Modbus/TCP/IP server from an AS400, or an oracle based system on solaris, or just about anything with sockets, with little effort. More to the point it would be quite easy to implement e.g. a modbus/TCP server in POSIX code that would easily adapt to any platform.
As has been pointed out, OPC was intended as an API and the use of DCOM to make it an enterprise wide access medium, is as everbody here points out, not satisfactory. That is why OPC proposed XML DA, but as this has been 'real soon now' for 2 years we cannot just sit back forever and say someday it will be arrive and it will work.
> A more practical approach is the is to leverage the technologies that the IT world has already embraced.
So instead of inventing a new protocol we leverage an existing one (modbus) which is capable of being used at an enterprise level and was designed as a master/slave protocol to allow computers to interogate field devices.
....switch......
open source and 'free' seem to have crept into this argument, not from me. If one actually read the title of the thread it implies nothing of the sort. I regard OPC to be an open protocol, and I do not mind paying for OPC products (heck, I have spent several thousand Euro over the last few months on various installations). I said they are in the doldrums because they are not coming up with goods they promised (despite the money).
On a final note I do not like the fact that many people claim that it is not OPC's fault that users attempt to use their 'API' for enterprise wide networking. We are festooned with OPC literature **especially** from certain major players in the OPC field, which tout it as such, and have been doing so for years. They used to say DCOM, for the last 2 years they have been saying that DCOM is not suitable but their XML DA standard, allready in beta and about to be released is their enterprise protocol. Deadlines come, deadlines go.......
( Complete thread: http://www.control.com/1026171355/index_html )
Well I can access a Modbus/TCP/IP server from an AS400, or an oracle based system on solaris, or just about anything with sockets, with little effort. More to the point it would be quite easy to implement e.g. a modbus/TCP server in POSIX code that would easily adapt to any platform.
As has been pointed out, OPC was intended as an API and the use of DCOM to make it an enterprise wide access medium, is as everbody here points out, not satisfactory. That is why OPC proposed XML DA, but as this has been 'real soon now' for 2 years we cannot just sit back forever and say someday it will be arrive and it will work.
> A more practical approach is the is to leverage the technologies that the IT world has already embraced.
So instead of inventing a new protocol we leverage an existing one (modbus) which is capable of being used at an enterprise level and was designed as a master/slave protocol to allow computers to interogate field devices.
....switch......
open source and 'free' seem to have crept into this argument, not from me. If one actually read the title of the thread it implies nothing of the sort. I regard OPC to be an open protocol, and I do not mind paying for OPC products (heck, I have spent several thousand Euro over the last few months on various installations). I said they are in the doldrums because they are not coming up with goods they promised (despite the money).
On a final note I do not like the fact that many people claim that it is not OPC's fault that users attempt to use their 'API' for enterprise wide networking. We are festooned with OPC literature **especially** from certain major players in the OPC field, which tout it as such, and have been doing so for years. They used to say DCOM, for the last 2 years they have been saying that DCOM is not suitable but their XML DA standard, allready in beta and about to be released is their enterprise protocol. Deadlines come, deadlines go.......
( Complete thread: http://www.control.com/1026171355/index_html )