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CSE 144 Project Part 3

Implement a routing tool for standard cell design that starts with placement results and specifies positions of wires connecting pins. The tool includes regular-net routing and feed-through routing and considers fabrication models. It solves problems using channel routing algorithms and handles exception cases. The output specification format includes net positions and track numbers.

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CSE 144 Project Part 3

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  1. CSE 144 ProjectPart 3

  2. Overview Goal: Implement a routing tool for standard cell design Routing tool: • Starts with the placement results • Specifies positions of wires that connect pins

  3. 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

  4. 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

  5. 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

  6. 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 horizontal&vertical constraints of feed-throughs • Solution: proceed to regular-net routing immediately, and ignore feed-through wires in regular-net routing phase

  7. Output Specification Format Net i : (PinPosition1, PinPosition2,...) [LeftmostPosition, RightmostPosition] TrackNumber

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