Experimental Physics and
Industrial Control System

Peregrine McGehee <[email protected]> · Mon, 1 Apr 1996 12:37:39 -1000

Chip, 
	Thanks for the update...

[email protected] writes:
 > Peregrine,
 > 
 > Here's my take on cdev & CA for new servers:
 > 
 > 1) if you need simple access to named variables (read/write/monitor), and
 >    want to use existing EPICS applications, use CA/PCAS.  This is nearly
 >    ready now.  You can still use cdev/CA on the client side if you want
 >    the added functionality of cdev (device oriented API, high level objects
 >    soon to come -- collections, lists, ..., and access to non-CA servers).
 > 
 > 2) if you need to transport complex data types, or perform any kind
 >    of transaction processing, and don't need EPICS applications, use cdev.
 >    This is available now, and it is not too hard even to implement a
 >    custom server starting from Walt's skeleton.
>
 > 3) if you want your cake and eat it too, and can wait a year, use cdev.
 >    I expect most major EPICS clients to support cdev in that sort of time
 >    frame.
 > 
Actually, this time frame is OK with us. We are just starting on
the CA/PCAS? based portion of a new control system but will need to
interface to an existing (non-EPICS) data acquisition system sometime
in 1997. 

 > 4) if you want it all now, boy are you unrealistic!
Agreed - we don't want it all now but we need to know the future
directions for planning being done now...

 > >The conclusions drawn from the above discussion seemed to be that
 > >1) it's simpler to interface a new service to PCAS (and use the CA +
 > >cdev? on the client side), but
 > >2) it's simpler to interface an old service to cdev.

 > Actually, it is just as simple to implement a new service using cdev, but
 > the ACE protocol doesn't have all the features of CA (connection management).
 > It does have other features, though.  So, I would re-frame the discussion
 > in terms of what you are trying to accomplish.  CA and cdev/ACE address
 > different needs.
Our situation is driven by several different goals:
	o EPICS/CA seems to be suited for the low-level control system
and engineering access.
	o cdev may help us in interfacing to our old data acquisition
system (which will probably never being converted to EPICS). This is
the interface that requires the types of services that cdev offers, 
especially transactions processing.

Pere.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System