[Halld-cal] Draft f250 data words for comments

[David Lawrence]

Hi Elton,

  I would argue in favor of Beni’s point. In order to correctly subtract the event-by-event pedestal
from the integral you will at least need to know the ratio of the number of samples used for each.
Since you have 15 unused bits in the pedestal word, you could use these to hold this information.
If you run in a mode where the 3rd word is dropped, you’ll be using average pedestals that were
presumably measured via pulse integral values so you won’t need the number of samples in
that case. 

Regards,
-David

On Jul 22, 2015, at 10:18 AM, Elton Smith <elton at jlab.org> wrote:

> Hi Beni,
> 
> Yes. This would be necessary if the integral uses a variable number of samples. From Mark's studies it appears that an integral over about 16 samples may be optimal at least for the bcal.
> 
> Thanks, Elton.
> Elton Smith
> Jefferson Lab MS 12H3
> 12000 Jefferson Ave STE 4
> Newport News, VA 23606
> (757) 269-7625
> (757) 269-6331 fax 
> On 7/22/15 9:00 AM, Beni Zihlmann wrote:
>> unless the pedestal sum contains the same number of samples as the integral 
>> it would be necessary to also store the sample numbers in the pedestal sum
>> and/or integral.
>> 
>> cheers,
>> Beni
>> 
>> 
>>> Dear colleagues, 
>>> 
>>> We have been discussing various considerations for the next f250 firmware upgrade. Based on the size of the spring data with mode 7, we see that the data volume is dominated by header words and not the "content" per se. Therefore, it appears that we should be able to handle the GlueX rate with 3 words for the calorimeter "content". However, it would be desirable to separate the pedestal into one word, which could be dropped if size becomes an issue. Attached is a draft scheme for discussion that achieves these goals. 
>>> 
>>> Feedback is welcome. 
>>> 
>>> Cheers, Elton. 
>>> 
>>> 
>>> 
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>> 
>> 
>> 
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