XIA Pixie-4 Express, User Manual, Page: 27 / 76

PIXIE-4 User’s Manual V2.69
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XIA 2015. All rights reserved.
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The hit pattern is a bit mask, which tells which channels were read out plus some additional
status information, as listed in table 4.4. After the event header follows the channel information
as indicated by the hit pattern, in order of increasing channel numbers. For example, if bits[3:0]
= 1001, the event header is followed by data from channel 0, then channel 3.
Table 4.4: Hit pattern bit description.
Bit # Description
0..3 If set, indicates that data for channel 0..3 have been recorded
4..7 4: Logic level of FRONT panel input
5: Result of LOCAL coincidence test
6: Logic level of backplane STATUS line,
7: Logic level of backplane TOKEN line (= result of global coincidence test), see section 7
8..11 If set, indicates that channel 0..3 has been hit in this event
(i.e. if zero, energy reported is invalid or only an estimate)
12..15 Logic level of the GATE input of channel 0..3 (for Rev. D modules only).
The data for each channel are organized into a channel header of length CHANHEADLEN,
which may be followed by waveform data. CHANHEADLEN depends on the run type and on
the method of data buffering, i.e. if raw data is directed to the intermediate Level-1 buffer or
directly to the linear buffer. Offline analysis programs should therefore check the value of
RUNTASK, which is reported in the buffer header. All currently supported data formats are
defined below.
1. For List Mode, either standard or compression 1, (RUNTASK = 256, 257),
CHANHEADLEN=9, and the nine words are
Table 4.5: Channel header, possibly followed by waveform data.
Word # Variable Description
0 CHAN_NDATA Number of words for this channel
1 CHAN_TRIGTIME Fast trigger time
2 CHAN_ENERGY Energy
3 CHAN_XIAPSA XIA PSA value
4 CHAN_USERPSA User PSA value
5 Unused N/A
6 Unused N/A
7 Unused N/A
8 CHAN_REALTIMEHI High word of the real time
Any waveform data for this channel would then follow this header. An offline analysis
program can recognize this by computing
N_WAVE_DATA = CHAN_NDATA- CHANHEADLEN.
If N_WAVE_DATA is greater than zero, it indicates the number of waveform data
words to follow.
In the current software version, the XIA PSA value contains the result of the constant
fraction trigger time computation (CFD). The format is as follows: the upper 8-bit of
the word point to the ADC sample before the CFD, counted from the beginning of the
trace. The lower 8 bits give the fraction of an ADC sample time between the sample