CAEN V767 128 Channel Gen. Purpose MH TDC - Physics

02/07/2003 V767 User's Manual – Rev.4
1.2. PRINCIPLES OF OPERATION
The V767 operating principles are based on the functionality of the CERN/ECP-MIC
TDC chip [2]. Five different module setups are selectable via software for different
acquisition scenarios, namely:
• Stop Trigger Matching;
• Start Trigger Matching;
• Start Gating;
• Continuous Storage;
• Common Stop Emulation.
It is possible to switch from one operation setup to the other by simply resetting and
reprogramming the module (with this operation the data in memory will be lost).
1.2.1. STOP TRIGGER MATCHING
An Event consists of the group of HIT signals that reach the enabled channels within a
time window of programmable width and relative position with respect to the common
TRIGGER signal. This operating setup does not foresee the use of the common START
signal.
0
EVENT
1 2 3 4 5 6 7 8 9
HIT ch[0..127]
0
1
window
TRIGGER
T_r
Fig. 1.2: Stop Trigger Matching Sequence
The stored data can be either an absolute time measurement (the zero time reference is
represented by the RESET) or a relative time measurement referred to the beginning of
the TRIGGER window (T_hit - T_r). The event is stored in the local buffer of the board
with the following structure:
HEADER event n. 0
DATUM n.1 HIT time(4)
DATUM n.2 HIT time(5)
DATUM n.3 HIT time(6)
DATUM n.4 HIT time(7)
DATUM n.5 HIT time(8)
EOB num. of data read = 5
There is no limit to the number of words in an event. If the total rate of HIT signals is
higher than the transfer rate of the data from the TDCs to the local buffer (or from the
local buffer to the VME) an overflow condition will be flagged by the relevant bit in the
Status Register (also by a front panel signal and LED). In this case there will be a data
loss.
Please refer to § 5.9 to see a simple C-like language example to operate in Stop Trigger
Matching mode.
NPO:
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