Wire ordering for detailed routing

Abstract

In many automatic routing systems, the wiring area is broken into a number of regions. A detailed router, such as a channel or switch-box router, routes each region separately. A junction pin is placed on a region boundary whenever the path of a wire crosses to another region. The way these junction pins are placed can be either a boon or a detriment to the economy of the routing. An algorithm that determines a consistent order for the junction pins that avoids unnecessary wire twisting is presented. If wires have to cross, the algorithm selects the intersection that would least affect the chip area and places the pins in the corresponding position. Experimental results obtained by using the algorithm in a macrocell placement and routing system that uses a contour-based, gridless channel router to perform detailed routing in the regions are presented. >