From: Frank Geurts (geurts_at_rice.edu)
Date: Tue Feb 11 2003 - 00:08:04 EST
John,
are you available somewhere tomorrow so Zhangbu and I can call. The
issue still revolves around getting the pvpd east and west coincidences
available at the STAR trigger. You know who things are currently set up
(fanning out the EAST and WEST signals, and sending them on a 40ns cable
to Zhangbu's stuff). As it turns out the signals arive too late ...
zhangbu sees them in the zdc post one clock tick. Meaning that we are
too late by at least some 40ns (Zhangbu??). I couldn't see any timing
measurements on your trigger logic diagram for the path from the output
of the ps706s until the outputs of the EAST or WEST coincidence units.
* What would you guess this timing would be?
* From the diagram I read that we had enough outputs for both
coincidences so we could provide Zhangbu with regular negative logic,
right? Or did we give him positive logic (w/ a pulsewidth of 20ns)?
In order to push the timing back, we could reconsider removing the fan
unit which we placed to protect ourselved from reflections. I suppose
removing the cable to that unit + the unit itself could safe us 8ns
(cable length?) + 6-7ns (transient time, according to specs for the
LC428) about 15ns. Not much, but maybe Zhangbu can get his 40ns cable
somewhat shorter too ...
In any case, the reflections for which the fan-out unit should protect
us could also be minimized by a attenuator in Zhangbu's signal path.
Currently, he already has an 14dB attenuator in it.
With the scheduled access, we just want to ran with you through some
options before we touch anything. Maybe we could use the TOF phone
bridge so Bill and Geary can join if they want to (if these guys can
keep their meeting short :) ... )
-frank
This archive was generated by hypermail 2.1.4 : Thu Jul 24 2003 - 00:39:34 EDT