Experimental Physics and
Industrial Control System

Zenon Szalata <[email protected]> · Fri, 10 May 2013 12:14:29 -0700

Hi Andrew,

On 05/10/13 11:08, Andrew Johnson wrote:

Hi Zenon,

On 2013-05-10 Zenon Szalata wrote:

The hardware registers are read/write.
When the IOC starts, the register has some value previously set.
After IOC init, I issue a series of dbpf commands, one for each register.
These trigger processing a record that reads the register.
After the register is read, the read value is put into the output record
with NPP.

The record you showed was Soft Channel though, was this what you're calling an
an output record?  I see that it does have a forward link.

Yes, it is a longout record, so I called it output.

These are Beckhoff bus terminal records which are a bit complicated to
read from and especially to write to.  To have it work correctly, I need
to insert a 0.2 second delay between dbpf commands.
I decided to use NPP because the output record, although it is soft
channel, when processed will result in the value being written back to
the register, which should be harmless, but I wanted to avoid it,
because significantly more delay would be needed.

Unfortunately for most record types doing a dbPut() to the VAL field without
processing the record will *not* trigger a CA monitor for the field.  If the
VAL field is PP(TRUE) the code in dbPut() assumes that puts to the field will
cause the record to be processed and that processing will trigger a monitor,
so it doesn't do one itself to avoid sending an unnecessary double update.  In
your case though you're not processing the record, so EDM never gets sent an
update even though subsequent caget or dbpr commands do show the new value.

I started this thread after observing that EDM was singling out one

particular record and always the same one. Number of similar records

were handled the same way and their values made it to the Text

Controls. Also, relaunching the EDM was not enough to get the correct

value. Just this morning I discovered that restarting the EDM program

would get the correct value. I was strongly convinced and no longer am

that closing a screen (one of many control by an EDM program) resulted

in CA disconnect to all PVs referenced by that screen. I thought that

just putting the screen in question in a debug mode and then back in

execute, would also do CA disconnect/connect or at least the correct

values would be obtained. This was not happening. Well, I am still

confused by this whole thing.

If this is really the cause of my difficulty, I will think how to modify
the records such that the target output record gets the value and gets
processed and somehow writing back to the register will be suppressed.
I was trying to avoid the extra complication.

The SDIS link of the subsequent record might be useful here.

- Andrew

Thanks Andrew,
Zen

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System