Experimental Physics and
Industrial Control System

Dear colleagues
	Here at LIGO we are setting up a Beckhoff EtherCat-based slow control system that we communicate with from our control-room through EPICS.  

We are using the BESSY-developed EPICS OPC server to provide the interface.  
The configuration is a Windows7 PC running both the EtherCat PLCs and the EPICS-OPC servers.
We use a recent EPICS-OPC release (based on 3.14.2)

We have followed BESSY guidelines regarding database settings and run multiple iocShells for EPICS-OPC that each have ~1000 channels (total is about 20,000 channels)

We are seeing the following problem.
 1) Change EPICS variable for switch in control room
 2) Change is transmitted to Beckhoff OPC quite rapidly and switch is changed on EtherCat OPC(< 1 sec).
 3) Change in EPICS readback of OPC variable is slow, takes about 4 seconds (varies 2-6 seconds) even on EPICS client run on same Windows7 box

( This becomes even more fun when using a slider control in the control room…)

Has anyone else seen this behavior?

Should we move the EPICS-OPC server to a separate computer (but same LAN) as EtherCat OPC computer?
Should we run each EPICS-OPC iocShell in its own virtual Windows environment?

	Thanks
		Keith Thorne
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Keith Thorne <[email protected]>
CDS Software Engineer
LIGO Livingston Laboratory
Livingston, LA 70754
Phone: (225)686-3168 Fax: (225)686-7189