April 2003
Why not read the Data Acquisition at ANU
user guide? If you just cannot manage that at least read these selections.
The raw data received
from the MEGHA electronics via the f2vb
is processed in the data acquisition processor (vme1) and reformatted
using the standard MIDAS data format (see http://npg.dl.ac.uk/documents/edoc073/edoc073.html)
before writing to tape. Sunsort now has a data format MIDAS which can
handle this data. You should now find
that Sunsort reports zero errors when processing this data.
The method of sending
data from the data acquisition processor (vme1) to the tape server has been
changed to use a TCP network connection
which allows much higher data rates. In
online mode (data source = REMOTE) Sunsort must run in the same workstation as
the tape server (charissa1).
All the Charissa equipment at ANU is now connected
to a secure network and accesses the Internet via a firewall. This should make
no difference to outgoing connections but incoming connections are restricted
by the firewall to a limited set of permitted connections. See the network
connection section in the Charissa Computers at ANU document.
Login to charissa1
and start Sunsort in the usual way. Select format MIDAS (not megha)
and select sort media Remote.
In order to
run Sunsort in online mode data must be transferred from the data acquisition
system (vme1) to the tape server which must be in the GO state.
To get data for Sunsort – start the experiment writing to tape OR if tape output is not required then while in STOP state go to the Tape Control window and select No Storage. Then GO.
Remember to disable No Storage when you are ready to write data to
tape.
A useful diagnostic is started by the F2VB menu item in the Diagnostics menu This enables you to spy on the buffer RAM of the F2VB module and see your raw data. Very useful when the electronics is not working to its normal efficiency.
Ensure the option button shows display data RAM and click on the read button. 64 32 bit words of the data RAM are displayed. You can set the start address offset or enable the increment RAM address checkbox to step through the data RAM.
A useful button is Dump using current addresses which reads the data ram at the buffer address currently being written. [be careful if the data rate is VERY slow or stopped as the dump may show old data]
The format data RAM button will generate a formatted display of the last block of the data RAM displayed using the selected format option (make sure this is correct for your hardware but the default is for MEGHA electronics). Look for excessive amounts of bad data which would suggest that your electronics needs attention.
No data? -
Check that you have beam!! Check that
you are GOING!! If you are sure check
the F2VB state.
Check that event storage active is enabled (ticked)
If not – check that you really are Going
If it is then
If List ended and Memory full are not on permanently (ticked) [use redisplay to update] and FIFO empty is ticked then the electronics is not sending data to the f2vb
If it is and List ended is set permanently and FIFO empty is not
ticked then you may have a data acquisition system problem.
At the present time the system cannot create all
640 8K channel histograms required and so all options are equivalent to None.
However 2 histograms (Stat & Rate) are created which show the
activity on a data item basis.
Megha crate 1 increments into channels 64 ->
127; Megha crate 2 increments into channels 128 -> 191 etc.
Within a crate block the order is Ch0 E, Ch0 T,
Ch1 E etc.
The Rate histogram shows the increment
rate / sec for the Stat histogram and so is a very useful check on the
adcs.
To obtain a
printout of the amplifier settings for your run book. Select Act on Crates? All; click on Show
Settings and then use Ctrl+P to
print the contents of the window containing the settings display.
Useful data quality statistics are
available by selecting the Statistics menu item from the Monitoring
menu on the Experiment Control window. If the ratio of data word
skipped to total data words or the ratio of events not acceptable
to events is high then the electronics should be checked. It may be
useful to use the f2vb diagnostic option.
Total
data words number of data words (16 bit)
read from the f2vb
Events number of good events found
Event
not acceptable total number of events which contain
some type of serious error and are discarded
Bad
flag bits a data word which is
not a end of block or event header in which the label part flag bits are not
001 and the data part flag bits are not 100 [ie data word is not 0x2xxx8xxx]
Missing
start token all data words received when a start
event token is expected
Missing
stop token all data words discarded when the
end of data buffer is reached but there is a current partial event.
Data
after stop token all data words discarded when the end
of block token is received but there is still data in the data buffer
Data
word skipped a count of the total number
of data words discarded for any of the
reasons given. This can be compared with the Total data words received.