Overall trigger timing

Timing Scheme

From Elliott: Below is my current understanding (4pm 21-Jul-2006) 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
290 ns	Tagger MOR reaches BCAL crates	150 ns + 138.5 ns new cable, see Tagger trigger timing
235 ns	BCAL PMT signals reach discriminators	20 ns in PMT plus 100 ns cable
265 ns	Discriminator sum outputs arrive at trigger logic	30 ns in discriminators is a guess
265 ns	MOR arrives at trigger logic	Delayed to match discriminator sum outputs
295 ns	Trigger reaches trigger supervisor	Guess 30 ns coincidence logic plus cable
340 ns	L1 accept available at TS	45 ns internal trigger supervisor
390 ns	earliest that ADC gate can be active	50 ns ADC gate generation, cables to ADC crate, ADC internal
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 125 ns between the MOR and the BCAL crates. Note that at 80 ns we need to delay MOR by 35 ns to match the discriminators, so 115 ns should work fine. But we might as well put in a fast cable as it costs little more and buys us some headroom.

If we have to delay the ADC signals 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

(Zisis' comment referred to am earlier scheme, now superceded...ejw)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

(my comment also referred to the older scheme, now superceded...ejw)
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 150 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