W. Badgett, S. Dasu, M. Jaworsky, J. Lackey, W. Smith
University of Wisconsin
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The CMS Calorimeter Level 1 Regional Trigger is designed to process
up to 9728 energy values provided by the CMS calorimeter readout every
25 ns in a pipelined, deadtimeless manner.  The regional trigger
identifies electrons, isolated electrons, jets and provides sums of
transverse and missing transverse energy.  This digital system consists
of nineteen double-sided 9U VME crates and three types of PC boards:
eight receiver cards, eight electron identification, and one jet summary card per crate.  The cards in each crate communicate via a custom, high-speed backplane.

A prototype crate has been built with a backplane supporting VME transactions in all slots, with two standard 6U VME slots and eighteen special slots for the data processing cards.  In each special slot there are auxilliary connectors for data processing transfers between the cards, with up to 340 signals per card.  One prototype receiver card and one prototype electron identification card have been built and tested in this crate.  Inter-card data transfers at 160 MHz with point-to-point differential ECL signals have been successfully performed with these prototypes.

The operation of the receiver card energy summing trees has been
verified at the full operational speed of 160MHz.  Each receiver
card contains three custom designed 8x13 bit Adder ASICs, all of which
have functioned well in on-board tests.  In addition, the use of
high-speed 3ns ECL memories as look-up tables on both boards has
proven successful.

A premier feature of the regional trigger is its ability to perform
pattern recognition on the energy deposits in order to identify
electromagnetic type energy clusters, both isolated and non-isolated.
Through the use of look-up tables and a custom designed ASIC on
the electron identification card, we can find electron/photon candidate
objects in the calorimeter.  The electron identification ASIC provides
two independent programmable streams of electron candidates, with and
without isolation requirements.

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We present results from tests of the CMS Calorimeter Regional trigger
prototype electronics, including prototypes of the 9U VME double-sided crate, the receiver card and the electron identification card.   We describe the performance of the prototypes, including 8x13 bit custom Adder ASIC, the pipelined dataflow and the communication between the cards across the high-speed backplane.  We also describe designs of the other trigger ASICs, including the electron identification ASIC which incorporates an improved pattern recognition algorithm for finding electrons and photons.

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