Nomenclature Conventions

Detector Orientation and terminology

The following diagram shows the terminology used in the current DAQ

Parameters used

pldelay

This is the acronym for 'Pipeline Delay'. When the trigger signal goes high, the contents of the delay-line are recorded for final readout. This parameter is a tool to ensure that the data stream in delay-line comes within the right time-window of the trigger decision. The value of this parameter sets the time after which the signal from delay line is presented at the Pattern-buffer for readout. This time would be set close to the time expected for trigger formation. If this is set to (say) 225 ns, then a copy of the reconditioned signal is held back for 225 ns and is then presented at the pattern-buffer.

PWTL

This is an acronym for the 'Pulse-Width of Trigger Logic'. A copy of the reconditioned signal is sent to the trigger logic. This parameter sets the width of the signal going into the Trigger-Logic. This width hence sets the coincidence time. If this is set to (say) 100 ns, we are allowing a time window of 100ns for the trigger condition to be fulfilled by the pulses from different planes.

PWDL

This is an acronym for 'Pulse-Width of Delay Line'. A copy of the reconditioned signal is sent to the delay-line. This parameter sets the width of the signal going into the Delay-Line. This width in turn sets the time for which the signal to be sampled for readout is stretched. [PWDL should always be greater than or equal to PWTL, else we would be reading in data stream, which did not cause the trigger]

holdoff

This is the time for which the pulses coming from an individual strip are blocked after receiving a "valid" pulse.

minwidth

The pulses which are shorter than the value set by this parameter will not be considered a "valid pulse" and will be rejected right away in the input-stage (reconditioning block) without any further processing.

eventtrig

This parameter sets the number of planes(out of 4) that are required to register a signal at the same time, in order to form the event trigger.

accumtrig

This parameter sets the number of planes(out of 4) that are required to register a signal at the same time, in order to form the accumulation trigger.

Conventions followed in the Firmware

All physical entities are numbered from 1(not from 0), though in software, all counts start from 0.

chc: Compton Hall C
s1: slave 1 v1495
s2: slave 2 v1495
s3: slave 3 v1495

The diamond based electron detector setup uses 4 planes of the detector. The detector plane on the upstream side is termed 'plane 1' and the plane counts up, with the last plane termed plane 4.

Each detector has a total of 96 strips, which are being processed in groups of 32 strips each, termed as the top, middle and bottom groups of 32 strips go to s1, s2 and s3 respectively.

Among the strips of the detector, the strip which is closest to the main beam is termed 'strip 1' and is counted upwards.

Flags File

In the electron detector Flags file, for setting the appropriate mask values, you would need to know:

p1t : plane 1, top 32 strips    ; the top-most strip is the strip closet to the beam (going to A-port, slave 1)
p1m : plane 1, middle 32 strips (going to A-port, slave 2)
p1b : plane 1, bottom 32 strips ; the bottom-most strip is that which will be farthest from beam (going to A-port, slave 3)
p2t : plane 2, top 32 strips    (going to B-port, slave 1)
p2m : plane 2, middle 32 strips (going to B-port, slave 2)
p2b : plane 2, bottom 32 strips (going to B-port, slave 3)
p3t : plane 3, top 32 strips    (going to D-port, slave 1)
p3m : plane 3, middle 32 strips (going to D-port, slave 2)
p3b : plane 3, bottom 32 strips (going to D-port, slave 3)
p4t : plane 4, top 32 strips    (going to E-port, slave 1)
p4m : plane 4, middle 32 strips (going to E-port, slave 2)
p4b : plane 4, bottom 32 strips (going to E-port, slave 3)
   

a value of '1' enables the strip, '0' disables it. The mask values are set in groups of 32, it can be entered in either hex or integer value (but not binary) example:

 If strip 1 is to be masked off on plane 1, 
 strip 24 is to be masked off on plane 2
 strip 47 is to be masked off on plane 3
 all strips on plane 4 to be left active
 leaving all other strips active on all planes; then we have to put: 

---

 p1b = 0xfffffffe, p1m = 0xffffffff, p1t = 0xffffffff
 p2b = 0xfff7ffff, p2m = 0xffffffff, p2t = 0xffffffff
 p3b = 0xffffffff, p3m = 0xffffbfff, p3t = 0xffffffff

---

Glossary

cluster: a group of 8 strips being ORed together to get a trigger decision. 

The following short-hands have been used very often in parameters/variable names that a User may deal with.

PW: Pulse Width          Rd: read
TL: Trigger Logic        Wr: Write
DL: Delay Line           clk: clock
HO: HoldOff              DIN: Data Input
GE: Good Event           Buf: Buffer
MB: Master Board         Stat: statistics