Creating physical connections to all the logical connections present in the design with the help of metal layers is known as routing.
What are the types of routing?
- PG Route: Power/Ground physical routing is completed during floorplan. Secondary PG routing happens just after STD cell placement.
- Clock Route: Clock physical routing is completed during CTS after clock buffer insertion.
- Signal Route: All the signal routing are completed after all the cells are placed which is called as routing stage.
What are the pre routing checks?
- All the Physical cells and Standard cells should be placed properly inside the core area.
- Clock cells should be placed and clock routing should be completed. Clock NDR should be applied for the required or all clock nets.
- Acceptable congestion, Timing (Setup/Hold), Power and Logical DRCs.
- We should fix all the assign statements where 1’b0 should be connected via TIE low and similarly 1’b1 should be connected to TIE high cell.
- ATPG and scan coverage should be proper. The entire design should have testability.
- PDN report (Low Power report) should be clean.
- Logical Equivalence should be clean.
- Max Tran, Max Cap, Max Load etc. violations should not be too high. Marginal can be handled during routing or ECO stage.
What are the goals of routing?
- Route all the signal nets with minimal physical DRCs.
- Optimize Data path logic for timing, DRCs and Power.
- Quality of route in a way, post route CTO is optionally performed.
What are the stages of routing?
- Global Routing
- Track Assignment
- Detail Routing
