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<== Date ==> <== Thread ==>
Subject: RE: Initial value readback from hardware into output records
From: "Mark Rivers" <[email protected]>
To: "Russell Redman" <[email protected]>, <[email protected]>, <[email protected]>
Date: Tue, 7 Dec 2004 12:34:45 -0600
Title: Message
Russell,
 
The features I was discussing only apply to generic device support for drivers that use the new asynDriver interfaces.  Since your drivers are not based on asyn, and you are not using the asyn generic device support, then this will not be a problem for you.  Nothing in EPICS base has changed in this regard.
 
If you begin to use asyn-based drivers, and you don't want the records to set the value during init_record you can:
- Use non-generic device support
- Write an asyn SIMULATION driver, that looks just like the real driver, but does not talk to hardware
 
Mark
 
-----Original Message-----
From: Russell Redman [mailto:[email protected]]
Sent: Tuesday, December 07, 2004 10:44 AM
To: Mark Rivers; [email protected]; [email protected]
Subject: Re: Initial value readback from hardware into output records

I am curious about a closely related issue that I fear will arise when  we try to upgrade our version of EPICS from 3.13.8 to use the newer software.  My code runs in both hardware and simulation modes to allow the software to be tested without having the hardware attached.  When the IOC boots, it does not know which mode it is supposed to be in.  The operator sets HARDWARE/SIMULATION mode flag, then runs an INITIALISE action to open communications with hardware or with the simulator, as appropriate.  Very bad things happen if the EPICS drivers attempt to read back values from nonexistent hardware, and I have put a considerable effort into the startup code to ensure that I/O records do not process on startup.

So here is my question: How can I PREVENT an output record from reading back a value during init_record from hardware that may or may not exist?

Cheers,
Dr. Russell O. Redman
Tel: (250) 363-6917 | Fax: (250) 363-0045
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Replies:
RE: Initial value readback from hardware into output records Ralph Lange
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