Difference between revisions of "Overall trigger timing"
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<td>385 ns<br></td> | <td>385 ns<br></td> | ||
<td>gate reaches ADC crate<br></td> | <td>gate reaches ADC crate<br></td> | ||
| − | <td>15 ns a guess cable plus gate generator plus cable<br></td> | + | <td>15 ns a guess, cable plus gate generator plus cable<br></td> |
</tr> | </tr> | ||
| Line 77: | Line 77: | ||
Thus I tentatively conclude the current cabling will NOT work. | Thus I tentatively conclude the current cabling will NOT work. | ||
| − | Two solutions are possible: shorten the MOR delay, or add delay to the ADC signals. The former is far | + | Two solutions are possible: shorten the MOR delay, or add delay to the ADC signals. The former is far preferable as it only involves one cable, whereas the latter involves 36 cables. But it is not clear how much we can shorten the MOR via a direct fast cable between the tagger and the BCAL trigger crates. |
I propose we proceed on the former. If the latter becomes necessary there are a few possibilities, including purchase of cables, cutting some of the unused 170 ns in half and installing new ends to give 80 ns delay cables, etc. | I propose we proceed on the former. If the latter becomes necessary there are a few possibilities, including purchase of cables, cutting some of the unused 170 ns in half and installing new ends to give 80 ns delay cables, etc. | ||
Comments are welcome... | Comments are welcome... | ||
Revision as of 16:22, 20 July 2006
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 |
| 215 ns |
BCAL PMT signals reach discriminators |
20 ns in PMT plus 80 ns cable |
| 245 ns |
discriminator sum outputs available |
30 ns a guess, but must be delayed before final AND in any case |
| 310 ns |
Tagger MOR reaches final AND logic |
230 ns + 80 ns? cable, see Tagger trigger timing |
| 310 ns |
discriminator sums reach final AND |
Delayed to match MOR |
| 325 ns |
result of final AND reaches trigger supervisor |
15 ns a guess through trigger logic |
| 370 ns |
trigger supervisor L1 accept ready |
45 ns internal to TS |
| 385 ns |
gate reaches ADC crate |
15 ns a guess, cable plus gate generator plus cable |
| 385 ns |
BCAL signals reach ADC crate |
20 ns in PMT plus 250 ns cable plus photon flight time |
Note that my calculation shows the ADC gate reaching the crate EXACTLY at the same time as the signals. This is not a good situation as any slip in timing cuts off the ADC. But also note that the 80 ns cable from the CLAS area to our crates is also a guess, perhaps 60 ns is correct. Even so this only gives us 20 ns to play with.
Thus I tentatively conclude the current cabling will NOT work.
Two solutions are possible: shorten the MOR delay, or add delay to the ADC signals. The former is far preferable as it only involves one cable, whereas the latter involves 36 cables. But it is not clear how much we can shorten the MOR via a direct fast cable between the tagger and the BCAL trigger crates.
I propose we proceed on the former. If the latter becomes necessary there are a few possibilities, including purchase of cables, cutting some of the unused 170 ns in half and installing new ends to give 80 ns delay cables, etc.
Comments are welcome...
