Experimental Physics and
Industrial Control System

[email protected] (Ralph Lange) · Tue, 17 Mar 1998 14:16:27 +0100 (MET)

Benjamin Franksen wrote:
> Perhaps it is worth mentioning that the SCAN field is not PP, so if you
> change it over CA you need to process the record (eg by a put to the
> PROC field) for the change to take effect.

Which is IMO not true, as the SCAN field is special by nature, i.e. scan
periodic list issues are taken care of automatically by database runtime
access. [See base/src/db/dbAccess.c if you _really_ want to know the
details.]

SCAN fields are accessible, i.e. you may change it any way you like (CA or
DB links). Keep in mind that --- as SCAN is of a MENU type --- you will
have to use the index number instead of the string at runtime.

Within the database (part)

---------              ----------
|       |              |        |
|       |  PP          |        |
|    VAL|<-------------|INP     |
|       |              |        |
|       |              |        |
---------              ----------
recSrc                 recDest

if recSrc.SCAN is set to Passive, each processing of recDest will process
recSrc before the recSrc.VAL is used.

Setting recSrc.SCAN field to something different from Passive will disable
this mechanism. recSrc will be processed according to its SCAN value.
When processed, recDest will use whatever recSrc.VAL contains at that time.
No additional processing is required.

Ralph

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System