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ALCT firmware

ALCT firmware. A. Madorsky University of Florida. ALCT trigger logic structure. Input d emultiplexor. Pulse extender. Pattern detector. Ghost cancellation. Best pattern selector. Output multiplexor. Input demultiplexor. Wiregroup hits come multiplexed at 80 MHz, 2 frames

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ALCT firmware

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  1. ALCT firmware A. Madorsky University of Florida

  2. ALCT trigger logic structure Input demultiplexor Pulse extender Pattern detector Ghost cancellation Best pattern selector Output multiplexor

  3. Input demultiplexor • Wiregroup hits come multiplexed at 80 MHz, 2 frames • Input demux unwraps them into a single 40 MHz frame Input bit Output bits CLK 40 MHz CLK 80 MHz

  4. Pulse extender • Wiregroup hits extended • Allows for overlap with extended hits from other wiregroups Original hits Extended hits

  5. Pattern detector • Detects patterns tied to one key wire group in layer 3 • Collision patterns are programmable within envelope • Collision and halo patterns detected independently • During entire first LHC run, collision patterns was matching envelope • Each pattern detector has dead time after valid pattern detection • 6 clocks • NOT entire ALCT, dead time is per pattern detector Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 Layer 6 Key wire group Collision pattern envelope Programmed collision pattern example Fixed halo pattern = wiregroupenabled for detection = wiregroup

  6. Ghost Cancellation Logic • Patterns next to actual track often fire with lower quality • GCL removes lower-quality neighbors of better quality patterns • Including delayed ghosts Ghost creation mechanism example Cancellation examples BX 0 BX 1 BX 2 Better pattern Q = 3 Ghost Q = 0 = inactive pattern key wiregroup = wiregroup = good quality pattern key wiregroup = wiregroupthat’s been hit = worse quality pattern key wiregroup

  7. Best pattern selector • Receives quality codes from pattern detectors • 32, 48, 64, 96, or 112 codes depending on chamber type • Finds two best patterns on each BX • “Colliding” search algorithm • Single clock latency First best search direction Second best search direction Second best pattern First best pattern = inactive pattern key wiregroup = good quality pattern key wiregroup = worse quality pattern key wiregroup

  8. Output multiplexor • Sends data to TMB in two frames at 80 MHz • Also includes TMB link diagnostic and error correction circuitry

  9. Latency

  10. Possible improvements • From VadimKhotilovich: • Use narrower patterns for ME1/1 chambers • Patterns are programmable in current firmware • No f/w modifications necessary, just reprogram the patterns • Modify Ghost Cancellation • Disable removing higher-quality patterns because of earlier low-quality patterns in the vicinity • Will increase latency by 3 clocks • Reduce dead time in pattern detector • Currently 6 clocks • All the above should be possible even in Virtex-E firmware

  11. Possible improvements in Spartan-6 • Stub timing is currently defined by pre-trigger (V. Khotilovich) • First 3 or 4 hits arriving = pre-trigger • Proposed to measure timing by median time of hits in wiregroups • Need more details on this • Multiple collision patterns • Second collision pattern used to exist in firmware for Virtex-E • Have been removed as unnecessary • May be useful in the future • Deeper DAQ buffer • Very straightforward • Suggestions are welcomed

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