S-bit & cluster timing
This is somehow a follow-up on issue #35, focusing on the lowest accessible data that can be read out from within the GEM system.
Basing ourselves on results from the OTMB, we trigger a calibration pulse once for 3 channels of the same VFAT (in order to avoid inter-VFAT avoid timing issues). The 3 channels correspond to adjacent pads which, after re-mapping, would from a cluster. We expected to see 1 cluster of size 2, on partition 1, address 23 (the channels are 26, 30, and 34 on VFAT 1, short chamber).
The results in [0] are quite different:
- We see via the hitmap that all 3 channels fire (no timing information)
- We see that the first valid cluster can be of size 0, or a split cluster
- We see that the S-bit monitor on the FE and the BE give the same data
The results are even more puzzling since channels 26 and 30 are on the same differential pair. Channel 34 is on the following pair.
Which test could be done to understand if the problem lies within the VFAT, the GEB, the S-bit sampling/alignment mechanism, or the clustering?
A possibility is to probe the S-bit differential pairs on the OH (not convenient). Another possibility would be to use a DRU-less S-bit sampling system.
[0]
Iteration 0
Hitmap - 0b00000000000000000000000000000000000000000000101010000000000000
FE - partition 1 - address 23 - size 2
BE - partition 1 - address 23 - size 2
Iteration 1
Hitmap - 0b00000000000000000000000000000000000000000000101010000000000000
FE - partition 1 - address 25 - size 0
BE - partition 1 - address 25 - size 0
Iteration 2
Hitmap - 0b00000000000000000000000000000000000000000000101010000000000000
FE - partition 1 - address 23 - size 2
BE - partition 1 - address 23 - size 2
Iteration 3
Hitmap - 0b00000000000000000000000000000000000000000000101010000000000000
FE - partition 1 - address 23 - size 0
BE - partition 1 - address 23 - size 0
Iteration 4
Hitmap - 0b00000000000000000000000000000000000000000000101010000000000000
FE - partition 1 - address 23 - size 0
BE - partition 1 - address 23 - size 0
Iteration 5
Hitmap - 0b00000000000000000000000000000000000000000000101010000000000000
FE - partition 1 - address 23 - size 2
BE - partition 1 - address 23 - size 2
Iteration 6
Hitmap - 0b00000000000000000000000000000000000000000000101010000000000000
FE - partition 1 - address 23 - size 2
BE - partition 1 - address 23 - size 2
Iteration 7
Hitmap - 0b00000000000000000000000000000000000000000000101010000000000000
FE - partition 1 - address 23 - size 2
BE - partition 1 - address 23 - size 2
Iteration 8
Hitmap - 0b00000000000000000000000000000000000000000000101010000000000000
FE - partition 1 - address 25 - size 0
FE - partition 1 - address 23 - size 0
BE - partition 1 - address 25 - size 0
BE - partition 1 - address 23 - size 0
Iteration 9
Hitmap - 0b00000000000000000000000000000000000000000000101010000000000000
FE - partition 1 - address 23 - size 2
BE - partition 1 - address 23 - size 2