1. CSE 144 Project Part 3

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

3. Routing Model Regular-net routing Feed-through 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