CAEN
Electronic Instrumentation
UM3148
–
DT5730/DT5725 User Manual rev. 2
29
Event Structure
The event can be readout via Optical Link or USB; data format is 32-bit long word (see
Tab. 9.3
)
An event is structured in:
•
Header
(four 32-bit words)
•
Data
(variable size and format)
Header
consists in 4 words including the following information:
•
EVENT SIZE (Bit[27:0] of 1
st
header word)
= It is the size of the event (number of 32-bit long words);
•
BOARD FAIL FLAG (Bit[26] of 2
nd
header word)
= Implemented from ROC FPGA firmware revision
4.5
on
(
reserved
otherwise), t
his bit is set to “1” in consequence of a hardware problem (e.g. PLL
unlocking or over-
temperature condition). The user can collect more information about the cause by reading at register address
0x8104 and contact CAEN Support Service if necessary (see §
14
);
•
Bit[24] (2
nd
header word)
= This bit identifies the event format; it is reserved and
must be 0
;
•
Bit[23:8] (2
nd
header word)
= Starting from revision
4.6
of the ROC FPGA firmware, these 16 bits can be
programmed to provide different trigger information according to the setting of the bits[22:21] at register
address 0x811C (
Tab. 9.2
).
Note:
for ROC FPGA firmware revisions lower than
4.6
. these bits are
reserved
.
REGISTER 0x811C
Bits[22:21]
FUNCTIONAL
DESCRIPTION
Bit[23:8]
(16 bits in the2
nd
header word)
00
(default)
Not used
Must be 0
01
Event Trigger Source
Indicates the trigger source causing the
event acquisition:
Bits[23:19] = 0000
Bit[18] = Software Trigger
Bit[17] = External Trigger
Bit[16] = 0
Bits[11:8] = Trigger requests from the
couple of channels (refer to §
Self-Trigger
)
10
Extended Trigger Time Tag
(ETTT)
A 48-bit Trigger Time Tag (ETTT)
information is configured, where Bits[23:8]
contributes as the 16 most significant bits
together to the 32-bit TTT field (4
th
header
word).
Note:
in the 48-bit TTT, the overflow bit is
not provided.
11
Not used
reserved
Tab. 9.2
:
TRG OPTIONS configuration table
•
CHANNEL MASK
(
Bit[7:0] of
2
nd
header word
) = It is the mask of the channels participating in the event. This
information must be used by the software to acknowledge which channel the samples are coming from.
•
EVENT COUNTER
(Bit[23:0] of 3
rd
header word)
= This is the trigger counter; it can count either accepted
triggers only, or all triggers.