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

Subject: Re: Logical Naming of Hardware Addresses
From: mrk@phebos.aps.anl.gov
Date: Wed, 25 May 94 12:42:18 -0500
Andrew Johnson talked about problems he had configuring reflective memory.
I have no already existing "correct" solution. However all of us involved
with ioc development recognize the problem and really want to come up with
a nice solution.

A couple of months ago there was a flurry of messages about this same topic.
I think that there was at least some agreement that what I am going to say
is correct (Jeff Hill and John Winans can be expected to scream if I am
wrong)

The basic idea is as follows:

In the existing database a link field can be one of the following:
1) constant
2) database link (reference to field of record in same ioc)
3) channel access link (reference to field of record in another ioc)
4) A hardware link. This can be one of several bus types, e.g. VME, GPIB, etc

The problem is hardware links. In general a device needs a lot more
information than is contained in a hardware link definition and presently
there is no place to define the additional info.

The solution is to replace hardware links by a reference to a new type of
record. This record can contain fields just like existing record types. The
difference is
1) The record has no database common
2) It is not processed.

For each device type the person providing device support provides an ascii
record definition for the device. This record can contain all the fields
needed to configure an instance of the device. For example a vme device record
would have fields to define all the info in the existing vme link definition.
The record could also contain any additional fields the developer decides
are needed.

Database Generation Tools would allow a user to create a record instance for
each device instance.

The existing link definitions would replace the hardware definitions by a
definition that allows the link to reference this new type of record, i.e.
this provides logical hardware links.

Marty Kraimer



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