Cronologic xTDC4, Руководство пользователя

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Coarse timestamp of the start pulse. Values are given in multiples of 1 . 6 ns.
unsigned int64 data[1]
TDC hits. the user can cast the array to uint32* to directly operate on the TDC hits.
# bits 31 to 8 7 to 4 3 to 0
content TDC DATA FLAGS CHN
The timestamp of the hit is stored in bits 31 down to 8. Bits 7 down to 4 are hit flags:
Bits 7 + 6: Timestamp consists of FPGA timing only with 1666 ps precision, as both the
TDC and the Carry Chain TDC missed this stop event.
Bit 7: FPGA did not see the stop event: hit may be out of sequence and may belong to
another group.
Bit 6: Timestamp consists of Carry Chain TDC timing only with 150 ps precision, as the
TDC missed this hit.
Bit 5: Time since start pulse is longer than timestamp counter range (218 µs ). If the timestamp
counter range is exceeded before the next occurrence of a stop event, a data[] element with bit 5
set which does not belong to a hit on any channel is added to the sequence of hits. The channel
number for this hit is set to 15. For each overflow of the timestamp counter in a group one such
data[] element is added to the group. The total offset of a hit can be computed by
∆ T
hit
= # bits
·
218 µ s + fine timestamp
where # bits counts the number of 5
th
bit occurrences until the hit shows up in the group. The
maximum counter range supported by the xTDC4 hardware is 13 , 975 µs .
Bit 4: Timestamp of the rising edge. Default is falling edge.
The channel number is given in the lowest nibble of the data word. A value of 0 corresponds
to channel A, a value of 3 to channel D. Values 7 to 14 are reserved and 15 denotes a group time
counter overflow.
cronologic GmbH & Co. KG 19 xTDC4 User Guide