MBBO record support

[Peregrine McGehee <mcgehee@cfht.hawaii.edu>]

Item 1.
We have noticed the following behavior in the MBBO record when we have
a constant DOL field.

In init_record:

If the DOL is a constant rather than a link, then it is fetched 
and written into the VAL field.

    if (pmbbo->dol.type == CONSTANT){
	pmbbo->val = pmbbo->dol.value.value;
	pmbbo->udf = FALSE;
    }

But later on within init_record() the VAL field is overwritten by
either raw or converted RVAL field if the DSET entry for init_record
exists.

Then in process:

If DOL is not a constant than we update the value. The code is:

	if (pmbbo->dol.type != CONSTANT && pmbbo->omsl == CLOSED_LOOP) {
	    long status;
	    unsigned short val;

	    status = recGblGetFastLink(&pmbbo->dol, (void *) pmbbo, &val);
	    if(status==0) {
		pmbbo->val= val;
		pmbbo->udf= FALSE;
	    }

The net effect is that VAL never has the value of DOL if DOL is a
constant.
 

Item 2.
Bob Dalesio mentioned that a field known as "IVAL" used to exist on
the MBBO record. The purpose of this field was to allow puts that were
not of type DBR_ENUM into the VAL field thus circumventing the
complaints from put_enum_string(). This is a useful feature if you
have no state strings and associated values defined (SDEF=0).

So far, only MEDM seems to cope with the current situation, all other
programs report an Illegal choice dbPutField error.


Peregrine

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Peregrine M. McGehee		Canada-France-Hawaii Telescope Corporation
(808) 885-7944			P.O. Box 1597, Kamuela, Hawaii