Cse 144 project part 3
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CSE 144 Project Part 3. Overview. Goal: Implement a routing tool for standard cell design. Routing tool: Starts with the placement results Specifies positions of wires that connect pins. Routing Model. Regular-net routing Regular nets: wires within each channel

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CSE 144 Project Part 3

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Cse 144 project part 3

CSE 144 ProjectPart 3


Overview

Overview

Goal: Implement a routing tool for standard cell design

Routing tool:

  • Starts with the placement results

  • Specifies positions of wires that connect pins


Routing model

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


Feed through routing

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


Regular net routing

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


Core algorithm and handling of exception cases

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


Output specification

Output Specification

Format

Net i : (PinPosition1, PinPosition2,...) [LeftmostPosition, RightmostPosition] TrackNumber


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