[Halld-tracking-hw] Tracking minutes posted

[Naomi Jarvis]

Hi Gerard,

David put together a draft document for the current spec - http://argus.phys.uregina.ca/cgi-bin/private/DocDB/ShowDocument?docid=2274

There the slot does come before the channel, and we have one large 15-bit chunk designated as quality factor which would include the pedestal.
I hadn't realized that the slot would also be in the block header.   

Could we take some of the 5 bits marked slot and move them into the QF section?  The extra space (QF would then be 20 bits) would allow for full precision pedestal in 12 bits, plus another 8 for quality indicators.  Also, we have 3 bits in the block header to designate data format, or rather, how to interpret the QF part.   I would hope that we would not go through more than 8 iterations of this but it could happen, and 1 or 2 bits of the QF section could be kept aside for this.  If we have full precision pedestal in the event readout then I don't think we would need separate pedestal runs. 

(Is there another header designating the crate which is tagged on separately?)

Best, 

Naomi.




On Jul 23, 2013, at 9:58 AM, Gerard Visser wrote:

> hi Dave,
> 	I think it might be better to provide a more generic and all-encompassing 
> redundancy in the data, such as by inserting a CRC word every N hits or at end 
> of block or something like that. Just a fixed pattern on a few bits is a pretty 
> minimalist sort of redundancy, e.g. would not detect if an even number of 
> longwords was dropped, for instance.
> 	I also suspect that more bits might be good for quality/status of the hit, 
> although I don't have a specific proposal. At the moment I see it is proposed 
> (1c) to have 13 bits for "pedestal"&quality (these are all quality bits IMHO). 
> This may eventually prove not to be enough, then the 5 slot bits could be added 
> into this purpose.
> 	Regardless of the slot bits, I think you are certainly right to put some 
> redundancy in the data that can be used for integrity check, so IMHO you should 
> add some CRC words explicitly for that purpose.
> 	Sincerely,
> 
> 		Gerard
> 
> p.s. Minor point: If you do keep slot field, how about putting it to the left of 
> channel field, so that the whole thing can be interpreted as a 12 bit 
> superchannel number? Of course the bit arrangement doesn't matter except to 
> improve human readability of the code and data.
> 
> 
> On 7/23/2013 1:14 AM, David Lawrence wrote:
>> 
>> Hi Gerard,
>> 
>>    That's correct, "slot" is the slot in the VME crate. You're right, it
>> could be sacrificed from the hit record if needed. Right now, it appears
>> in the both the block header and hit record and is currently used by the
>> parsing software to provide a small integrity check on the data. If
>> there is something else more worthy of those bits, we can consider
>> dropping it from the hit record.
>> 
>> Regards,
>> -Dave
>> 
>> On 7/23/13 12:47 AM, Gerard Visser wrote:
>>> hi Naomi, Dave,
>>> 	What is 'slot' by the way? (5/62 hit payload bits used for this.) I guess it is
>>> the ADC module number? But why put this in the hit record? It can just as well
>>> be in the block or event header from the module, it will be constant for all hit
>>> records from the module...
>>> 
>>> 	- Gerard
>>> 
>>> 
>>> On 7/22/2013 7:58 PM, Naomi Jarvis wrote:
>>>> Minutes are online at https://halldweb1.jlab.org/wiki/index.php/July_17,_2013_Tracking_CDC/FDC
>>>> 
>>>> Also I think I forgot to email the same for the previous meeting, sorry, those are at https://halldweb1.jlab.org/wiki/index.php/July_3,_2013_Tracking_CDC/FDC
>>>> 
>>>> Best regards,
>>>> 
>>>> Naomi.
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>>> https://mailman.jlab.org/mailman/listinfo/halld-tracking-hw
>> 
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