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<== Date ==> <== Thread ==>

Subject: Re: [No Subject]
From: Andrew Johnson <anj@aps.anl.gov>
To: "Sahin, Hakan" <hakan.sahin@desy.de>
Cc: tech-talk@aps.anl.gov
Date: Thu, 04 Jan 2007 11:50:05 -0600
Hi Hakan,

Sahin, Hakan wrote:
Hi,
I am a Labview User, and I create Records with Labview (version 8.0)

I am not a Labview user, so some of what I write might not apply directly to what you're used to, but I am describing the underlying EPICS database implementation.


I want to ask about the Data Type DBR_CTRL_XXXX.
When I create a Record, the Data Type of this Record will be created as
DBR_DOUBLE. Is it possible to change the Data Type of a Record
DBR_CTRL_DOUBLE with DBR_DOUBLE?

Record field types are not created with DBR_XXXX types but with DBF_XXXX types, which are more fundamental. There is no such thing as a DBF_CTRL_DOUBLE, and you can't create a record type with a VAL field of a compound type (a DBR_CTRL_DOUBLE is a compound type because it has multiple parts to it - the value and various other attributes such as the engineering units, precision, graphic limits etc.).


The DBR_XXXX types are used for making requests through Channel Access, and they actually cause the database to collect information from a number of fields in the record into the structure that CA transports to your client. You can make a DBR_CTRL_DOUBLE request to almost any PV and you'll get back information appropriate to that record field. Where the various pieces of information comes from depends on the record type, but in general if you're getting the VAL field of a record the units attribute will come from the EGU field, the precision attribute from the PREC field, the graphic limits from the HOPR/LOPR fields and so on.

Why I'm asking this, because DBR_CTRL_XXXX is able to display: value,
alarm status, alarm severity, units, display precision, graphic limits,
and control limits of Record.

with command 'caget'.
For Example:
"caget PVName" gives out:
PVName   Value

"caget -d34 PVName" gives out:
value, alarm status, alarm severity, units, display precision(HI,LO),
graphic limits(HI,LO),
control limits(HI,LO,HIHI,LOLO).


Thanks.
Hakan Sahin

I'm not sure whether the above answers your question, but hopefully it will get you closer to understanding what's going on.


- Andrew
--
There is considerable overlap between the intelligence of the smartest
bears and the dumbest tourists -- Yosemite National Park Ranger

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