Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Thu, 20 Oct 2005 11:03:30 -0500

Marty Kraimer wrote:

Are you saying that we should not implement block, process, and wait

semantics as part of a link definition?

I am under the impression that the general concensus that it is a good

idea and we were deciding semantics.

Am I wrong?

I'm *not* against providing control over synchronization and sequencing

of links, especially when it comes to arrays of them, but I don't

believe all of the "block, process and wait" attributes make sense when

you're dealing with single links, especially when it comes to fields

like SDIS and TSEL.

Now I'm probably only complaining about some aspects of block and wait

here, since process obviously *is* a link attribute for the caPut/caGet

link types. I also accept that we need the ability to control whether

get/put operations on individual links cause the source record to wait

for the target operation to complete. However the descriptions I've

seen so far of what the "block, process and wait" attributes mean

haven't been very clear.

I suspect that the process attribute of a caMonitor link type actually

has a different meaning to that of a caGet (for caMonitor it controls

processing of the source record when a monitor event occurs, not the

processing of the target record) - am I right in that? If so, I would

really want to use a different name for it, something like updateScan?

I *am* saying that the complex sequencing and synchronization controls

should not be part of the basic link type itself, but are more logically

part of the array of links that the calc and sequence records etc.

actually implement. Instead of using an array of links, they could

contains an array of structures, where each structure contains a link

field plus some other fields that control the seq/sync controls for that

link. This would allow the sequence record to have even more complex

controls than calc, since it wants to allow the user to sequence input

and output links together in groups maybe, insert delays and so on.

I'd also like to see the discussion of the capabilities of individual

link types distinguished from that of the capabilities of the generic

link interface. A process attribute controls a capability of CA and DB

links, but means nothing to my xyzzy link type, so please don't make my

link have to implement stuff it doesn't need.

- Andrew
--
English probably arose from Normans trying to pick up Saxon girls.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System