Data analysis and trigger words and bits

Last updated: Wed Nov 19 10:22:07 CST 1997

During datataking information about trigger type was stored in camac data block along with other trigger status data: trigger labels (bits), amplitudes in scintillator counters, scalers, Programmable Logic Units and Memory Logic Units output patterns. All this info went into camac data block.
Data Aquisition System analysed trigger type and depending on event trigger type and information stored in dis database wrote event to one of the data streams: charm, primakoff or calibration. If trigger was not specially described it went to calibration stream. We had 2 crates (2 blocks) of camac data. First short block was taken for each event, this called 100% crate. The other block with more data was stored for some fraction of events, this is so called 1% crate (ratio is different from 1/100). Data for 1% crate independent of trigger type also were written to calibration stream.

Data flow

Raw data

Programm to read data from camac crate is on fn781a in
    $ONLINE_DIR/scc/crate_1.asm -- 100% crate
and set of saved files in this directory. This code defines which words and in which order were read and written to camac data stream.


Offline routine $OFF781_SRC/unpack_camac.F unpack raw camac data into common/camac_bk/ of $OFF781_INC/
There are 2 logical variables creadout_1 and creadout_2 which are true when data from crates 1 and/or 2 present. You can consult meaning of the camac data words here  or in comments in files unpack_camac.F or crate_1.asm or crate_2.asm. There are few latches, each bit or group of latch bits have special meaning:
  • 100% crate Latch A: T2 tags, misc.
  • 100% crate Latch B: T2 tags = t2_mlu_dec output
  • 100% crate Latch C: T1 triggers and tags               <--- TRIGGER TYPE
  • other camac latches
  • Most likely you looking this page to find out how to manage  trigger type.

    There is one more routine $OFF781_SRC/unpack_hodo.F which unpack scintillator hodoscope information into common/hodo_bk/ of OFF781_INC/
    Related OCS tables are hod_pos.ocs and hod_sz.ocs (includes also info for hodo unpack).

    Trigger type

    How it works

    We had 3 stage trigger: T0 fires T1, it maybe fire T2, then it maybe fire T2, which maybe start DAQ which write data into one of the data streams.
    Input information for trigger decision or result of logical function on which these decisions were based were stored.
    For each trigger level we might have several subtriggers, which of them fired this trigger level can be identified by trigger labels.
    To make picture more complex, let mension that we had several trigger logic definitions like Beam, Interaction, Pulser and different versions and derivatives. In this case meaning of bits and latches might be different between trigger types and versions, but we were trying keep basic definitions stable. Which trigger type was loaded for specific run was recorded in $CALIBRATION_DIR/trigger/trigger_load.log
    It also was recorded by DAQ in run log, which is now converted into runs database

    For given trigger type or version:

    In general, we should use for each run or group of runs or trigger type separate OCS table describing the trigger.
    1. Test T2 subtrigger type in Latch_A, 8 bits #9-12, unpacked to "camac_trig_b0" of common/camac_bk/
    2. Test T1 subtrigger type in Latch_C, 8 bits #1-08, unpacked to "camac_trig_b2" of common/camac_bk/
    As a practical matter, T2 was almost always (exept few dedicated runs) equal to T1 (fired, when T1 fired), and I can't gurantee that T2=T1_prescaled subtrogger bit was set to 1 in this case, that is we must analyse only T1 subtrigger type unpacked to "camac_trig_b2" , which in our case is a trigger type.
    These trigger words are copied (need to check with Jurgen which 'these words') by DAQ to hard_trig(3) of common /event_header/ of the $OFF781_INC/

    T1 subtrigger bit # to test T1 subtrigger type pattern described in first part of $CON781_DIR/kern/trigs.ocs table.
    There we have 8 triggers defined with bits (1-8 -- mask 1/2/4/8 etc.) for charm/Excl/He/T0-prescaled/Hyper/Dummy/HST/Reserved triggers. This raw camac dataword is unpacked to "camac_trig_b2" of common /camac_bk/ (file

    Trigger Types and Runs

  • List of triggers
  • List of triggers used to write data 

    Back to E781 trigger home page  return