Overall trigger timing
Timing Scheme
From Elliott: Below is my current understanding of the trigger timing for the BCAL test:
| Time |
What |
Comment |
| 0 ns |
Electron hits tagger foil |
|
| 115 ns |
Photon hits BCAL |
125 ns to alcove, but BCAL is about 10 feet upstream on the platform |
| 235 ns |
BCAL PMT signals reach discriminators |
20 ns in PMT plus 100 ns cable |
| 265 ns |
Discriminator sum outputs available |
30 ns a guess, but must be delayed before final AND in any case |
| 230 ns |
Tagger MOR reaches BCAL crates |
150 ns + 80 ns new fast cable, see Tagger trigger timing |
| 230 ns |
Discriminator sums available |
Delayed to match MOR |
| 260 ns |
Trigger reaches trigger supervisor |
Guess 30 ns coincidence logic |
| 305 ns |
L1 accept available at TS |
45 ns internal trigger supervisor |
| 355 ns |
ADC gate active | 50 ns ADC gate generation, cables to ADC crate, ADC internalbr> |
| 435 ns |
BCAL signals reach ADC crate |
20 ns in PMT plus 300 ns cable plus photon flight time |
The above timing works if we can get less than xxx ns (80 ns is target) between the MOR and the BCAL crates. If not we will have to add delay to the ADC signals. If so there are a few possibilities, including purchase of cables, cutting some of the unused 170 ns in half and installing new ends to give 85 ns delay cables, etc.
Comments
(comment below referred to earlier scheme, now superceded...ejw)
I agree that this will not work. I also agree on the plan of action, in the following priority: 1) Try to shorten MOR, 2) Cut unused 170ns cable (if there are enough and if this is ok with folks like Richard) and 3) Purchase new cables. -- Zisis
21-Jul...preliminary measurement of the RadPhi cables gives 100 and 300 ns, not 80 and 250 ns. If correct we gain an additional 50 ns delay. If we run a new MOR cable (save 66 ns) we gain a total of over 100 ns. This should be adequate to cover items missing above (patch cables, additional logic delays not accounted for yet, etc). I propose we still plan to run a new MOR cable even if the signal cables are 50 ns longer. -- Elliott
21-Jul...everything updated based on latest understanding -- Elliott
