Experimental Physics and
Industrial Control System

Dirk Zimoch <[email protected]> · Mon, 05 Jul 2010 08:02:23 -0000

Andrew,

> The aao record always goes to INVALID_ALARM in simulation mode.
I missed that. It should use the SIMS field as well. As soon as I get bazaar installed on this computer, I will fix that.

I have never seen documentation on the aai/aao records, but I guess that the intention was to set BPTR directly to memory mapped register space to save the time for copying data. But this has several disadvantages:
* BPTR must be set early enough (fixed now)
* BPTR must not change at run time (e.g. no double buffering). I have to check what devExtend() does to solve this problem.
* As a result, BPTR may contain inconsistent data if the hardware modifies the buffer while it is being read (e.g. by a CA read or monitor)

I kept the memory allocation model to stay compatible to old device supports. Additionally I allow for new device supports not to set BPTR. Also to stay compatible, I do not want to switch from BPTR to VAL.

Basically the aai is the same as the waveform record except that it does not have a RARM field. The aao is the only record that is intended to write arrays. (The waveform can write through its INP if the device support allows. But if we do so, why do we need ai/ao, mbbi/mbbo, etc. pairs?)

-- 
https://code.launchpad.net/~dirk.zimoch/epics-base/fix-aai-and-aao/+merge/26195
Your team EPICS Core Developers is requested to review the proposed merge of lp:~dirk.zimoch/epics-base/fix-aai-and-aao into lp:epics-base.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System