TDC Raw Data Format
Hardware: MTDC-64, TDC-96, PhTDC
See also: VME DAQ Rawdata Format
Data read out of the TDC is contained in 32 bit data packets. The first four bits of a packet are used to define the type of data packet. The following 4 bits are used to identify the ID of the TDC chip (programmable) generating the data. Only 8 out of the possible 16 packet types are defined for TDC data (bit 31 always set to zero by TDC). The remaining 8 packet types are added by higher levels of the DAQ system.
Data types |
|
0 |
|
1 |
|
2 |
TDC header |
3 |
TDC trailer |
4 |
TDC leading edge time measurement |
5 |
TDC trailing edge time measurement |
6 |
TDC error |
7 |
Padding (ignore it) |
2 - TDC event header |
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31 |
30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
19 |
18 |
17 |
16 |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
2 |
TDC ID |
event number |
TDC timestamp |
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TDC ID is the programmed ID of TDC
TDC timestamp in number of 25 ns time intervals since global trigger timestamp found in event header.
3 - TDC event trailer |
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31 |
30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
19 |
18 |
17 |
16 |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
3 |
TDC ID |
event number |
TDC word count |
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Time measurement data format depends on resolution set.
4, 5 - Single edge measurements (normal resolution, 19 bits) |
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31 |
30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
19 |
18 |
17 |
16 |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
4/5 |
TDC ID |
channel |
time measurement |
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- data type: 4 - leading, 5 - trailing.
- channel - TDC channel number, 0 to 31
- time measurement - leading or trailing edge measurement in programmed time resolution
4, 5 - Single edge measurements (25 ps, very high resolution, 21 bits) |
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31 |
30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
19 |
18 |
17 |
16 |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
4/5 |
TDC ID |
channel/4 |
time bits [1:0] |
time bits [20:2] |
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- data type: 4 - leading, 5 - trailing.
- channel/4 - TDC channel number, 0 to 7 (should be multiplied by 4)
4, 5 - Combined leading and trailing measurement, pairing mode (not used in VMEDAQ) |
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31 |
30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
19 |
18 |
17 |
16 |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
4/5 |
TDC ID |
channel |
width |
leading time |
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- width - pulse width in programmed time resolution
- leading time - leading edge measurement in programmed time resolution
6 - TDC error |
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31 |
30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
19 |
18 |
17 |
16 |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
6 |
TDC ID |
reserved |
TDC error flags |
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TDC error flags bits:
- [0] Hit lost in group 0 from read-out fifo overflow
- [1] Hit lost in group 0 from L1 buffer overflow
- [2] Hit error have been detected in group 0
- [3] Hit lost in group 1 from read-out fifo overflow
- [4] Hit lost in group 1 from L1 buffer overflow
- [5] Hit error have been detected in group 1
- [6] Hit lost in group 2 from read-out fifo overflow
- [7] Hit lost in group 2 from L1 buffer overflow
- [8] Hit error have been detected in group 2
- [9] Hit lost in group 3 from read-out fifo overflow
- [10] Hit lost in group 3 from L1 buffer overflow
- [11] Hit error have been detected in group 3
- [12] Hits rejected because of programmed event size limit
- [13] Event lost (trigger FIFO ovefrlow)
- [14] Internal fatal chip error has been detected
Most important error bits are 12 and 13. Error bit 14 should be ignored.
For detailed description of TDC please refer to HPTDC manual.
7 - Padding |
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31 |
30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
19 |
18 |
17 |
16 |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
7 |
0 |
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