Citect OPC tagging

Hi,

I am new to citect and i am trying to create some tags to access objects of an OPC Server. What do i need to fill in the address portion of a variable tag in citect to access an object of an opc server?

thanks

Bloody OPC - if you are using a PLC use the Citect driver and forget OPC - it is an absolute pain and Citect do not do OPC very well, although there is a new, much better Citect OPC driver coming out. I HATE OPC!!! Had some bad experiences.

Funnily enough this is exactly what the last Citect tech guy i spoke to told me too, do Citect admit their OPC implementation is not up to scratch or is it a case of their PLC and device drivers are that much better ?

Both!!!

Makes me happy that we are using the Modbus TCP driver then !!

I would always prefer to use a driver that is written specifically for the task - provided it is written and debugged properly.

OPC is slow and clunky as far as I am concerned. Had bad experiences with a BACnet OPC server that cost me a bomb. It used to take up to 10 minutes to scan an Alerton BMS system before it started to work properly. The one good thing about it is that it can then be used on the basis of detecting change of state and this does speed things up quite a bit but still slow to me and not fully reliable.

The other major problem with the BACnet system is that it runs as a TCP/IP layer and if IT decide to re-program the switches it does not work anymore. This happens to one of my clients all the time where there are lots of Siemens PLCs all connected to a Citect SCADA on Ethernet. IT fiddle with the network on the weekend and Citect can no longer find the PLCs. You would have the same problem with Modbus TCP by the way - IT can really stuff the system up. That is one of the reasons for using a proprietary token ring network - IT do not want to know about it.

BobB said:

You would have the same problem with Modbus TCP by the way - IT can really stuff the system up.

Click to expand...

Oh yeah, been there done that !!

We tend to take ownership of the Modbus PLC network where we can and give access to Citect via webclients from the IT (company)owned network.

Some people dont want extra hardware in there so insist on VLAN'ing it off on their own network, take down one switch for maintenance and the hey presto the PLC's disappear !!