September 9, 2003

TileCal Coincidence Board

We plan to build a few PCBs to allow us to trigger the calorimeter on cosmic rays.

The properties of the board are as follows:

9U 400mm VME board

o VME interface for control and status readback

input from 48 towers at top of detector and 48 towers at bottom

for initial use of the coincidence board the input signals are received from an adapter board placed in the same crate

o adapter board has 50-pin input connectors for trigger cables from detector

o sorts and distributes tower signals to output connectors to coincidence board

o input signals to adapter board are differential

o output signals from adapter board are differential so coincidence board can be used later with signals from the official LVL1 receiver boards

input is set of differential signals

o analog signals shaped by 3in1 cards

o FWHM ~80 ns (because of slow cables)

o typical signal amplitude 20 mV

o maximum noise ~10mV for 20Mhz BW

signals should be processed to reduce bandwidth to ~20 Mhz (variable?)

o this is to reduce noise

signals must be discriminated with variable threshold between 5 mV and 50 mV

o set with DAC via VME

o make available on front panel monitor point

after discrimination signals should have standardized widths

o use 25 ns TTC clock period and sync to next clock edge

Kelby suggests width of x+25ns width where x jitters but is < 25ns

o note that input signal may be longer than shaped signal

do two-fold coincidences between corresponding towers

o scale coincidence rate for each pair

o use table to specify which towers to enable in coincidence

do OR of all tower pairs and output NIM signal from front panel

VME control for

o setting threshold

o setting bandwidth limit (?)

o setting coincidence matrix

o outputting coincidence rates

Board would use EPLD and have VME interface

We should make 5 such boards

Two are needed in Nov. 2003