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<div class="moz-cite-prefix">Hi Naomi, everybody, <br>
<br>
I finally looked through all the back and forth on this issue and
more or less understand<br>
the last iteration of the data format. So here my 0.5 cent
blabla:<br>
<br>
0) As you point out the pedestal position/width changes if a cable
is connected to the ADC or not and<br>
also where the cable is coming from (pream source) because all
this matters to the overall ground<br>
and capacitive coupling that is seen by the ADC channel.<br>
that is why we need to monitor the pedestal at all times and
needs to be in the data.<br>
<br>
1) 12 Bits for the pedestal is overkill. As you write below we
want to have the pedestal as reasonably<br>
low as possible to maximise the dynamic range of the ADC. An
offset of 0x8000 puts that pedestal<br>
roughly in the middle of the full range of the ADC but there
is quite a large variation from channel <br>
to channel. In the FDCs I observe base lines easily vary
between 2500 and 5000 or even more.<br>
(note these numbers are with the traditional factor 4 ! ;-) )<br>
The offsets should be set such (for each individual channel)
that it is sufficiently high above zero to<br>
accommodate the noise. This means it has to depend on the
width of the pedestal (noise), lets say<br>
for the sake of argument an offset above zero is 4 sigma of
the pedestal. I can not remember what <br>
the answer was to the question "what happens to the ADC when
the input signal undershoots the<br>
low edge of the dynamic range?"<br>
Note that the pedestal is normalized to one sample.<br>
From this considerations the pedestals in the proposed data
format can easily be expressed with 8 bits.<br>
<br>
2) we do not need special pedestal runs, what we need is special
runs reading out all samples with the offsets<br>
all set at 0x8000 or some other most preferred offset. From
that data one can easily calculate the pedestals<br>
and width and from that new best offsets. These new offsets
can then be loaded and the procedure repeated<br>
to verify/optimize the settings if so desired.<br>
-> which of course brings up another point of book-keeping
these pedestals, width and offsets and what is<br>
currently loaded in the ADCs.<br>
<br>
<br>
3) I think it is a very bad idea to have different data formats
for the FDC and CDC. We have to come up with<br>
a common solution. The threat of a potential mix-up in the
future overweights any benefit I see.<br>
<br>
4) The next very important step is now to understand what
algorithms we want to implement to determine<br>
pedestal, integral and time. I guess this is the harder part.
We have to specify what we want and find<br>
out what we can get ;-) (We can't always get what we want but
we can try). <br>
-> I propose for the next tracking meeting to have a
discussion of what we want. We should try to start<br>
with the basics (simple approach with expansion in mind)
and then go from there to see how far we <br>
can push the system.<br>
<br>
<br>
cheers,<br>
Beni<br>
<br>
<br>
<br>
<br>
<br>
<br>
</div>
<blockquote cite="mid:C970103D-3CFB-4DEE-91B4-6BABFB9CA236@cmu.edu"
type="cite">
<div>Hello, </div>
<div><br>
</div>
<div>OK.</div>
<div><br class="webkit-block-placeholder">
</div>
<div>Yes using all 12 bits would indicate a huge problem, pedestal
should really be in a much smaller range such as between 40 and
80, could be higher if on the tail end of a previous event. If
it moves (and stays) outside that range you need to know where
it is in order to correct the offset on the flash. I am finding
that the pedestals change when I switch electronics or read out
a different set of straws. Also the pedestal rises (and gain
falls) if the preamp LV supply drops, which is a good indicator
of a bad cable at the HVB end. So we would need full range
readout at least for setting the pedestals following maintenance
and for periodic monitoring; this could be done using a
dedicated pedestal data format rather than in the pulse data
format.</div>
<div><br>
</div>
<div>Naomi.</div>
<div><br class="webkit-block-placeholder">
</div>
<div><br class="webkit-block-placeholder">
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<div>On Jul 23, 2013, at 11:08 AM, David Lawrence wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">
<meta content="text/html; charset=ISO-8859-1"
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<div bgcolor="#FFFFFF" text="#000000"> Hi All,<br>
<br>
To answer your last question first: Yes, the crate number
(rocid) is included in an EVIO header that is put on by the
ROC before the data is sent over the network. The ROC may
send more than one "Physics Event Bank" for a block of
events (e.g. multiple DMAs are used), but the number will
generally appear just once or twice for all hits in all
events in the block.<br>
<br>
As for the pedestal, wouldn't this indicate a problem if
the pedestal itself was a large enough number as to require
12 bits? I thought from earlier discussions we were going to
try and adjust the pedestal so that it was never larger than
say, a 9 -bit number could hold (0-511). This would leave 6
bits for the Q.F. Not that I'm completely opposed to
dropping the slot from the hit data, but I do like how it is
currently being used to help check the data integrity in a
stream-like fashion which helps supplement the other checks
being done with larger data chunks.<br>
<br>
Regards,<br>
-David<br>
<br>
<div class="moz-cite-prefix">On 7/23/13 10:43 AM, Naomi
Jarvis wrote:<br>
</div>
<blockquote
cite="mid:863CB2AD-C6DA-46FB-94DD-827FA6A48951@cmu.edu"
type="cite">
<div><span class="Apple-style-span"
style="border-collapse: separate; font-family:
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separate; font-family: Helvetica; font-style:
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<div style="word-wrap: break-word;
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<div>Hi Gerard,</div>
</div>
</span><br class="Apple-interchange-newline">
</div>
</span>David put together a draft document for the
current spec - <a moz-do-not-send="true"
href="http://argus.phys.uregina.ca/cgi-bin/private/DocDB/ShowDocument?docid=2274">http://argus.phys.uregina.ca/cgi-bin/private/DocDB/ShowDocument?docid=2274</a><br
class="Apple-interchange-newline">
</span><br class="Apple-interchange-newline">
</div>
<div>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.</div>
<div>I hadn't realized that the slot would also be in the
block header. </div>
<div><br>
</div>
<div>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. </div>
<div><br>
</div>
<div>(Is there another header designating the crate which
is tagged on separately?)</div>
<div><br>
</div>
<div>Best, </div>
<div><br>
</div>
<div>Naomi.</div>
<div><br>
</div>
<div><br>
</div>
<div><br class="webkit-block-placeholder">
</div>
<br>
<div>
<div>On Jul 23, 2013, at 9:58 AM, Gerard Visser wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">
<div>hi Dave,<br>
<span class="Apple-tab-span" style="white-space:pre">
</span>I think it might be better to provide a more
generic and all-encompassing <br>
redundancy in the data, such as by inserting a CRC
word every N hits or at end <br>
of block or something like that. Just a fixed
pattern on a few bits is a pretty <br>
minimalist sort of redundancy, e.g. would not detect
if an even number of <br>
longwords was dropped, for instance.<br>
<span class="Apple-tab-span" style="white-space:pre">
</span>I also suspect that more bits might be good
for quality/status of the hit, <br>
although I don't have a specific proposal. At the
moment I see it is proposed <br>
(1c) to have 13 bits for "pedestal"&quality
(these are all quality bits IMHO). <br>
This may eventually prove not to be enough, then the
5 slot bits could be added <br>
into this purpose.<br>
<span class="Apple-tab-span" style="white-space:pre">
</span>Regardless of the slot bits, I think you are
certainly right to put some <br>
redundancy in the data that can be used for
integrity check, so IMHO you should <br>
add some CRC words explicitly for that purpose.<br>
<span class="Apple-tab-span" style="white-space:pre">
</span>Sincerely,<br>
<br>
<span class="Apple-tab-span" style="white-space:pre">
</span><span class="Apple-tab-span"
style="white-space:pre"> </span>Gerard<br>
<br>
p.s. Minor point: If you do keep slot field, how
about putting it to the left of <br>
channel field, so that the whole thing can be
interpreted as a 12 bit <br>
superchannel number? Of course the bit arrangement
doesn't matter except to <br>
improve human readability of the code and data.<br>
<br>
<br>
On 7/23/2013 1:14 AM, David Lawrence wrote:<br>
<blockquote type="cite"><br>
</blockquote>
<blockquote type="cite">Hi Gerard,<br>
</blockquote>
<blockquote type="cite"><br>
</blockquote>
<blockquote type="cite"> That's correct, "slot"
is the slot in the VME crate. You're right, it<br>
</blockquote>
<blockquote type="cite">could be sacrificed from the
hit record if needed. Right now, it appears<br>
</blockquote>
<blockquote type="cite">in the both the block header
and hit record and is currently used by the<br>
</blockquote>
<blockquote type="cite">parsing software to provide
a small integrity check on the data. If<br>
</blockquote>
<blockquote type="cite">there is something else more
worthy of those bits, we can consider<br>
</blockquote>
<blockquote type="cite">dropping it from the hit
record.<br>
</blockquote>
<blockquote type="cite"><br>
</blockquote>
<blockquote type="cite">Regards,<br>
</blockquote>
<blockquote type="cite">-Dave<br>
</blockquote>
<blockquote type="cite"><br>
</blockquote>
<blockquote type="cite">On 7/23/13 12:47 AM, Gerard
Visser wrote:<br>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">hi Naomi, Dave,<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite"><span
class="Apple-tab-span" style="white-space:pre">
</span>What is 'slot' by the way? (5/62 hit
payload bits used for this.) I guess it is<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">the ADC module number? But
why put this in the hit record? It can just as
well<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">be in the block or event
header from the module, it will be constant for
all hit<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">records from the module...<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite"><br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite"><span
class="Apple-tab-span" style="white-space:pre">
</span>- Gerard<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite"><br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite"><br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">On 7/22/2013 7:58 PM,
Naomi Jarvis wrote:<br>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite">Minutes are online at <a
moz-do-not-send="true"
href="https://halldweb1.jlab.org/wiki/index.php/July_17,_2013_Tracking_CDC/FDC">https://halldweb1.jlab.org/wiki/index.php/July_17,_2013_Tracking_CDC/FDC</a><br>
</blockquote>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite"><br>
</blockquote>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite">Also I think I forgot to
email the same for the previous meeting,
sorry, those are at <a moz-do-not-send="true"
href="https://halldweb1.jlab.org/wiki/index.php/July_3,_2013_Tracking_CDC/FDC">https://halldweb1.jlab.org/wiki/index.php/July_3,_2013_Tracking_CDC/FDC</a><br>
</blockquote>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite"><br>
</blockquote>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite">Best regards,<br>
</blockquote>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite"><br>
</blockquote>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite">Naomi.<br>
</blockquote>
</blockquote>
</blockquote>
<blockquote type="cite">
<blockquote type="cite">_______________________________________________<br>
</blockquote>
</blockquote>
<blockquote type="cite">
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