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This document discusses the potential of a combined architecture for ECAL and HCAL in the challenges of SLHC, and the compatibility of the uTCA architecture with high-bandwidth, flexible interconnects. It also addresses legacy mismatch issues and the importance of clock, slow control, and fast control for SLHC.
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Calorimeter Trigger+Readout Hardware in a uTCA Architecture-- Some Thoughts -- Jeremiah Mans – University of Minnesota CMS SLHC Trigger Workshop – Nov 29, 2007
Thoughts for Consideration • A combined architecture bringing together ECAL and HCAL early and performing local seeding should be very powerful for the challenges of SLHC • The uTCA architecture is a nice match to the needs for high-bandwidth, flexible interconnects. • LHC-specific issues: • Legacy links to front ends – some “suboptimal” choices were made in the original designs which we may have to live with • Fast controls and clock distribution are important for LHC SLHC Trigger Workshop -- Calo Readout+Trigger in uTCA
Legacy mismatch • uTCA is designed for very high speed serial interconnects (2.5 Gbps data) • Existing ECAL and HCAL links are much slower (0.8 Gbps /1.2 Gbps) – with a symmetric system, we can’t feed in the data fast enough to keep the 2.5 Gbps links full (assuming 1-1 in/out) • Upgrades may be unlikely – difficulty and risk associated with complete detector disassembly (required for ECAL upgrade) • Ideal design for a receiver/calculator card should take into account the inherent asymmetry: more input links than output links for example SLHC Trigger Workshop -- Calo Readout+Trigger in uTCA
Clock, Slow Control, Fast Control • Critical clocks • LHC Bunch Clock – for pipelined calculations • Deserializer reference clocks : current HCAL links require LHCx2 frequency reference • Fast control • TTC will hopefully be replaced by a higher-bandwidth trigger/fast control system for SLHC capable of transmitting more information (partial trigger mask?, data destination tag?, etc) • Future implementation (in the counting room) is likely to be based on firmware within FPGAs rather than new ASICs • Slow control via Ethernet – independence from custom bus adapters! SLHC Trigger Workshop -- Calo Readout+Trigger in uTCA
Initial R&D Directions • Develop a clock-and-control receiver card • For the current version, use TTC as the fast control standard • Produce backplane clocks: LHC, 2xLHC (QPLL), crystal(?) • Possibly develop in MCH form-factor : also encorporate ethernet-switch chip • Free-toolchain for slow control development • Nice microcontrollers exist for Ethernet interface, but the development kit is rather expensive [should be relatively easy, since all toolchains seem to support gcc at the backend] • Goal: use vanilla uTCA as a starting point • We will probably want a custom backplane in the future, but if we stay compatible with the standard, we can easily test small systems, etc SLHC Trigger Workshop -- Calo Readout+Trigger in uTCA