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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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Presentation Transcript
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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