Hi,
Thanks Mark and Ralph I'll try it out and come back to you.
Best regards,
Hinko
Ralph Lange wrote:
> Hello Hinko,
>
> Some device supports, which are connecting to hardware capable of
> running in a multi-master setup, achieve this by processing the passive
> output record when a value update comes in from the hardware:
> In the interrupt handler, device support sets a flag in its private
> structure and issues a scan request for the record, i.e. it basically
> fakes the second part of an asynchronous operation. When the record is
> being processed, device support checks the flag and updates the record
> with the value from the hardware (instead of writing from the record to
> the hardware).
> Works flawlessly, does not need additional records, but of course
> doesn't solve the classic race condition when two masters (IOC and the
> other guy) try to write at the same time.
>
> Cheers,
> Ralph
>
>
> On Thu 11 Feb 2010 8:51:55 Mark Rivers wrote:
>> Hi Hinko,
>>
>> This is a classic problem of having more than one mechanism for
>> driving an output, and keeping the output PV up-to-date.
>>
>> Here is a database fragment that handles this logic (thanks to Tim
>> Mooney for this).
>>
>> FileNumber is the output record, the equivalent of the mbbo record in
>> your case. Note that it uses soft device support, it does not talk
>> directly to the hardware. FileNumber_RBV is the input record, the
>> equivalent of the mbbi record in your case. In my case it it I/O Intr
>> scanned, i.e. it processes when the hardware driver does a callback to
>> device support, but it could also be periodically scanned. There are 2
>> additional records required. FileNumber_write is the record that
>> actually talks to the hardware. FileNumber_Sync is a record that
>> copies the readback value from FileNumber_RBV to FileNumber, but
>> WITHOUT causing the value to be written to the hardware. It works
>> because the FileNumber_write record has scan disabled if the
>> FileNumber_sync record is processing (PACT=1). With this logic
>> FileNumber will correctly reflect the actual state of the hardware,
>> and it can also be written to change the hardware.
>>
>> record(longout, "$(P)$(R)FileNumber")
>> {
>> field(PINI, "YES")
>> field(OUT, "$(P)$(R)FileNumber_write PP")
>> field(VAL, "1")
>> }
>> record(longout, "$(P)$(R)FileNumber_write")
>> {
>> field(SDIS, "$(P)$(R)FileNumber_Sync.PACT")
>> field(DISV, "1")
>> field(DTYP, "asynInt32")
>> field(OUT, "@asyn($(PORT),$(ADDR),$(TIMEOUT))FILE_NUMBER")
>> }
>> record(longin, "$(P)$(R)FileNumber_RBV")
>> {
>> field(DTYP, "asynInt32")
>> field(INP, "@asyn($(PORT),$(ADDR),$(TIMEOUT))FILE_NUMBER")
>> field(SCAN, "I/O Intr")
>> field(FLNK, "$(P)$(R)FileNumber_Sync")
>> }
>> record(longout, "$(P)$(R)FileNumber_Sync")
>> {
>> field(DOL, "$(P)$(R)FileNumber_RBV NPP")
>> field(OMSL, "closed_loop")
>> field(OUT, "$(P)$(R)FileNumber PP")
>> }
>>
>> Mark
>>
>>
>
--
Hinko Kocevar
Technical support software engineer
Instrumentation Technologies
Velika pot 22, SI-5250 Solkan - Slovenia
T:+386 5 3352600, F:+386 5 3352601
mailto: [email protected]
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