A "Gridless" Variable-Width Channel Router for Macro Cell Design

In this paper, we present a channel router especially designed for routing macro cells. The router routes variable-width pins with wires of any width. Although the router uses a routing grid internally, it acts like it is completely gridless to the user. Pins along the top and the bottom edges of the channel can be at any X-location, and the router uses a channel compactor to compact all horizontal segments vertically. The router allows pins to be on either of the two routing layers. If all the power pins are on the same layer, the router routes the whole power bus in one single layer. It handles non-rectangular channels with highly irregular heights, and it also handles cyclic vertical constraints. Finally, the router has been tested with a number of industrial circuits.