Minutes of Interface Module Meeting 4/29-4/30/99
------------------------------------------------
4/29 meeting: Foglesong, Johnson, Matulik, Reay, Sidwell,
Zverev

Long discussion of resistive drops for power leads from 
sequencer to SVX. Right now total is projected to be 
2.75 ohms: with 1 ohm on interface module, 1.1 ohm on
3M cable, 0.4 on flex circuit (lo mass cable), and
0.3 ohms on HDI pig tail. This leads to a 1.2 v projected
drop on AVDD, and large swings on the chip digital power
(DVDD). Goal: 1.5 ohms; and as close to 0.5V drop as
possible. Separate power buss for low voltage was
suggested by Marvin.   


Drawings- no new drawings yet. John had a power supply
possibility with water-cooled enclosure which can handle
up to 10 pods per set (40A ea?), and 5 pod sets. Looks
good for LV and SVX power. Marvin is considering how to
get sense back so we can remove the effect of resistive
losses in the 3M cable.

Crate layout proposal presented by Sidwell, and available
from web page. Plan is that no modules see more than one
detector type- this costs more modules, but seemed 
sensible to most people.

Split bias voltages- requested by Lipton, briefly
discussed. Unpopular with most poeple (HV connections
double).

Next Meeting agenda- 

1) Drawings (JF)- issues of cable routing, space, 
card removal. Are there any show-stoppers? Is the
cutout thru the muon iron big enough?

2) Photovoltaic relays (MM)- tested with +200, saw 
< 0.1 nA current draw. Asked to test with -200 also.
These are used for HV (i.e. bias) voltage. Can we
pick a part number, and make a decision to go ahead?

3) Output cables (NRS, w RAS). Design is stalled because
we don't have a complete solution. NRS is asked to report
on the situation next Thursday. 

4) J1 backplane layout (Ben McD). How much room do we
have? What have we forgotten?

5) Split bias voltage (Ron Lipton). Ron is urged to
attend, and give the arguments for this. 

Cost is: a) double # HV lines and connects, b) double
# of relays, c) 34 conductor cable per board instead 
of 16, d) does the plan make sense, and do we really
extend the life of radiation-damaged silicon if we
can't do a 50-50 split.

6) Consensus on termination.
-----------------------------------------------------------
-----------------------------------------------------------
4/30 Meeting regarding terminations and cross-talk
-----------------------------------------------------
attendees: Johnson, Green, Utes, Zverev, DeMarteau,
Lipton, Sidwell

Purpose: settle on termination scheme for burn-in stands;
also trial for next interface module. How to reduce
cross talk, and get well-shaped signals in both 
directions.

The current situation was reviewed including old green 
card, and test beam. I will not summarize discussion.

Decisions:
1) For burn-in adopt Zverev proposal: --->>>DATA bus! <<<----
   a) add 82 ohm resistor to ground in SASEQ and big
sequencers
   b) on sequencer side of interface module, use 
Schottky pullup and pulldown diodes (no resistors).
   c) on HDI side - 75 ohm series resistor in series,
and schottky diodes pullup and pulldown.

2) Need to get ready for low-mass cable tests. A
box-full of adapters, cables, and boards are needed.
Can the Speedy zig-zag flex circuits be used?
Need short summary of logistics and parts (RAS or NRS?)

3) For Rev 3, leave in pads for series, pull-up, and
pull-down terminators (whether diode or resistive)


After the meeting there was a "show and tell" session
with the oscilloscope. Some anomalies were observed in
dvalid timing which are not understood. 
 Of interest is trigger on D7, and look at dvalid, and
clock. The timings are strange on current SASEQ and
setup.