[Halld-online] [Halld-level1] Data stream scalers, summary of the meeting

[Hovanes Egiyan]

The server that Sasha is talking about and  the EPICS
server  will not take much of the CPU time. The IOC will take about 1%
of a single CPU core. The only conflict is the access to the VME bus, which
will have to be done carefully.

The FADC scaler monitoring will need to be running continuously in the 
production
data taking mode  for detectors where we do not have JLab 
discriminators, for
instance in FCAL.

Hovanes.


On 01/23/2012 04:10 PM, Elliott Wolin wrote:
> Hi,
>
> Alex raises an important point.  ROC's must handle the full data rate
> and cannot have extraneous processes running on them that might
> interfere.  I've heard of a number of servers people want to see running
> on the ROC's, probably too many.  We have to carefully consider every
> process that runs on a ROC, and may need to combine the functionality of
> multiple servers into a smaller number (perhaps just one...).
>
> I will put this topic (servers) on the Online meeting agenda next week.
>
> Alex...I'd like to put you on the agenda next week to present the work
> on scalers you described in your email...let me know if you have a
> scheduling conflict.
>
> Thanks,
>
>
>
> On 01/23/2012 03:45 PM, Alexander Somov wrote:
>> Hi,
>>
>> The server runnning on the ROC might not be just an EPICS IOC,
>> but more complicated. It should handle messages/requests
>> from other debugging programs and provide an arbitrage for
>> accessing registers. For the trigger debugging I would not rely
>> on EPICS but just use 'standalone' debugging tools.
>>
>> At high rate we have to be sure that EPICS doesn't interfere with
>> the CODA readout (it should not, but has to be checked). Anyway,
>> the data stream scalers themself should provide a reasonable
>> online dq/monitoring tool.
>>
>> Cheers,
>>          Sascha
>>
>>
>>
>> Hi Dave,
>> There will be scalers that will be available for monitoring
>> programs. These registers will be written and readout independent
>> of CODA DAQ. This info is going to be available in EPICS for general
>> purpose monitoring.
>> Whenever there is a need, we will have EPICS IOC running on the VXS
>> crates CPU.
>> At least that is the plan.
>> Hovanes.
>>
>> On 01/23/2012 01:32 PM, David Lawrence wrote:
>>> Hi Sasha,
>>>
>>>       Are they counting even when the DAQ system is not currently taking
>>> data? I would think we would want an out-of-band way of getting at the
>>> scalers. That way, we can display them at any time (e.g. while tuning
>>> the beam in between runs). Maybe you mentioned something about this
>>> before...?
>>>
>>> -Dave
>>>
>>> On 1/23/12 1:25 PM, Alexander Somov wrote:
>>>> Hi Elton,
>>>>
>>>> A good point.
>>>>
>>>> You don't need to disentangle the whole events.
>>>> Scalers will have a tag in the fadc event block;
>>>> one will need to search for the corresponding tags
>>>> only; should be straight forward.
>>>>
>>>> Cheers,
>>>>             Sasha
>>>>
>>>>
>>>>
>>>> On Mon, 23 Jan 2012, Elton Smith wrote:
>>>>
>>>>> Hi Sasha,
>>>>>
>>>>> Thanks for the summary. In mode a) can easily scan through a file and
>>>>> pick out the events with scalers (without disentangling the whole
>> event)?
>>>>> Elton Smith
>>>>> Jefferson Lab MS 12H5
>>>>> 12000 Jefferson Ave
>>>>> Suite #16
>>>>> Newport News, VA 23606
>>>>> (757) 269-7625
>>>>> (757) 269-6331 fax
>>>>>
>>>>>
>>>>> On 1/23/12 9:10 AM, Alexander Somov wrote:
>>>>>> Hi,
>>>>>>
>>>>>> I brief summary of the data stream scaler
>>>>>> implementation  discussion last Friday
>>>>>> (Jan 20th, 2012):
>>>>>>
>>>>>> 1. Scalers will be integrated into the data readout
>>>>>> block of each FADC; they will be readout using DMA.
>>>>>>
>>>>>> 2. There are two ways of the implementation:
>>>>>>         a) scalers will be added to the last event in
>>>>>>            the block. A user needs to specify the block
>>>>>>            prescaling factor, i.e., the number of blocks
>>>>>>            after which the scalers should be added
>>>>>>            (for instance, add scalers in each 10000's readout
>>>>>>            blocks).
>>>>>>         b) Scaler readout will be handled by the special
>>>>>>            trigger type generated by the TS (the trig2 line
>>>>>>            going from the TI to the fadc can, for instance, be
>>>>>>            used for the scaler trigger distribution). Similar
>>>>>>            to a), scalers will be added to the readout block.
>>>>>>            Implementing this mode will require more efforts.
>>>>>>
>>>>>> 3. Edd and Bryan will start implementing mode a).
>>>>>>
>>>>>>
>>>>>> Cheers,
>>>>>>             Alex
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