CSE 144 Project Part 3

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CSE 144 ProjectPart 3
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Overview

• Goal Implement a routing tool for standard cell
  design

• Routing tool
• Starts with the placement results
• Specifies positions of wires that connect pins

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Routing Model

• Regular-net routing
• Regular nets wires within each channel
• Fabrication model 2-layer VH model
• Feed-through routing
• Feed-throughs wires crossing multiple channels
• Fabrication model
• Separate (the third) metal layer for vertical
  wires
• Horizontal wires share the same layer with
  regular nets

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Feed-through Routing

• Goal Specify the assignment of horizontal
  feed-through wires to the channels
• Model each channel as a big track
• Problem solved using channel routing algorithm
• Pin locations may NOT necessarily be at the edges
  of the big channel

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Regular-net Routing

• Goal Specify the routing configuration within
  each channel
• A typical channel routing problem
• Routing process needs to take into account the
  feed-through wires
• Vertical feed-through wires
• Routed in a separate layer
• No contributions to horizontal/vertical
  constraints
• Horizontal feed-through wires
• Routed in the same layer with horizontal regular
  wires
• Contribute to horizontal constraints
• No contribution to vertical constraints due to
  the absence of pins

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Core Algorithm and Handling of Exception Cases

• Both stages modeled as channel routing problem
  --- the Yoshimura-Kuh algorithm is used
• Exception case loops in vertical constraints
• Solution output a message indicating the
  detection of the loop, and immediately proceed to
  the routing of the next channel
• In feed-through routing
• Possible exception case fixed channel (big
  track) quantity --- might be insufficient for
  fulfilling horizontalvertical constraints of
  feed-throughs
• Solution proceed to regular-net routing
  immediately, and ignore feed-through wires in
  regular-net routing phase

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Output Specification

• Format
• Net i (PinPosition1, PinPosition2,...)
  LeftmostPosition, RightmostPosition TrackNumber