[Halld-online] Asynchronous scaler readout in Hall D

[Vardan Gyurjyan]

Hi Elliott,
Any software application can become an Afecs component by being able to 
communicate through cMsg rcDomain.
Sincerely,
Vardan

Elliott Wolin wrote:
> Hi Vardan,
>
> Thanks, I was considering this, but need to learn more about Afecs 
> components.  Note that the shared memory has to be accessible by C 
> programs.
>
>
>
> On 02/07/2012 01:46 PM, Vardan Gyurjyan wrote:
>> Hi,
>> I will suggest making this process an Afecs component, that can be 
>> included into the Hall-D experiment control system. Being an Afecs 
>> component one can subscribe scaler information event not being part 
>> of the data production system ( for e.g. web or cellphone apps).
>> Regards,
>> vardan
>> On Feb 7, 2012, at 1:27 PM, Elliott Wolin wrote:
>>
>>> To all concerned with scalers in the Hall D Online,
>>>
>>> Hovanes, Dave and I met to consider many details of dealing with
>>> scalers. We propose the guidelines below. Note that these refer to
>>> normal data taking, not to code development/debugging efforts.  
>>> Further,
>>> the discussion below refers to asynchronous readout of scalers, not to
>>> how scalers are read out and inserted into the data stream.
>>>
>>>
>>> - the preferred method for reading scalers asynchronously (i.e. from
>>> registers) is to use a single process that writes to shared memory.
>>> This allows us to control resource usage on the ROC's and manage ROC
>>> processes.
>>>
>>> - this process is independent of the DAQ system. It should be the only
>>> processes that reads scalers from the registers, even the ROC code
>>> should not do this.
>>>
>>> - any other process that needs scaler data can get it from the shared
>>> memory. This includes an EPICS IOC process and perhaps other processes.
>>>
>>> - current thinking is to use an EPICS IOC to serve asynchronous scalers
>>> out to monitoring processes or to servers that bundle and then
>>> redistribute scaler and other data.
>>>
>>> - One question that arose was whether all crates should be part of the
>>> DAQ system. In particular, should the discriminator crates include a TI
>>> board, accept triggers, be part of the CODA DAQ configuration, etc?  In
>>> favor is the simplicity of putting discriminator scalers in the data
>>> stream and the fact that in this way it is possible to read scalers out
>>> of all crates at the same time.  The downside is that more crates will
>>> have to participate in the DAQ system and that there are other ways to
>>> get discriminator scalers into the data stream.
>>>
>>>
>>> Comments, questions, concerns...?
>>>
>>> Thanks,
>>>
>>> -- 
>>>
>>>                 Sincerely,
>>>                     Elliott
>>>
>>>
>>> ================================================================================ 
>>>
>>>
>>>
>>>   Those raised in a morally relative or neutral environment will hold
>>>             no truths to be self-evident.
>>>                
>>>
>>> Elliott Wolin
>>> Staff Physicist, Jefferson Lab
>>> 12000 Jefferson Ave
>>> Suite 8 MS 12A1
>>> Newport News, VA 23606
>>> 757-269-7365
>>>
>>> ================================================================================ 
>>>
>>>
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>