[Halld-tracking-hw] F125ADC what do we want / need

[David Lawrence]

Hi All,

   I spoke with Beni a little about this this morning since I am currently
working on the code that parses this for the online monitoring and
the offline. I have not been involved in any other discussions, but here
are some thoughts based on what I've seen in the F250ADC formats
and my discussion with Beni:

1.) It is not possible to fit both the sum and the pulse time into a single
32-bit word. The word must have at least 12 bits of info to define the
data type and channel number leaving only 20 bits for payload. Hits
in the F125 must therefore span two 32-bit words.

2.) The FADC250 has a specification where the pulse time and pulse
integrals appear as separate data types (i.e. they appear in separate
32-bit words). This allows the option of having a module output one
of these but not the other. In practice, we will probably never want to
do this, but thee spec. allows it. To see the spec, look here, but
be aware a few things in the headers have changed:

https://halldweb1.jlab.org/wiki/images/d/db/FADC_Data_Format_V2.pdf


3.) For the FADC125, we could decide to couple the two words and
eliminate redundant information such as the channel number,
pulse number, and slot. This frees up enough bits to record a 12bit
pedestal with every hit. I've drawn this out in the diagram below
labeled Option1: to show how we could pack the bits in a format
consistent with the spirit of the current F250 spec.

4.) We could also follow almost exactly the format of the F250 spec.
with the difference being that we need 7bits instead of 5 for the
channel number in the F125. I've drawn this up as Option 2:
below.

5.) We could also have something completely different from either
of these. In any case, we'll want the block header/trailer and
event header words to follow the standard format for JLab modules
whose current specification is here:

https://halldweb1.jlab.org/wiki/images/5/58/JlabModuleDataFormat.pdf




Regards,
-David

On 7/8/13 9:17 AM, Beni Zihlmann wrote:
> Hi All,
> we have to come up with a list of specifications of the data we
> want to have from the ADC. I would like to use this email to
> initiate a discussion and put this topic on the agenda of the
> next tracking meeting. By that time we should have a clear
> understanding of what is needed so that the experts Cody
> and Gerard can tell us what is feasible and what not.
>
> cheers,
> Beni
> _______________________________________________
> Halld-tracking-hw mailing list
> Halld-tracking-hw at jlab.org
> https://mailman.jlab.org/mailman/listinfo/halld-tracking-hw

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