A-Electronic design automation-How routers

work-circuit board pcb

How routers work

Many routers execute the following overall algorithm:

• First, determine an approximate course for each net, often by routing on a coarse grid. This step is called global routing, and may optionally include layer assignment. Global routing limits the size and complexity of the following detailed routing steps, which can be done grid square by grid square.

For detailed routing, the most common technique is rip-up and reroute:

• Select a sequence in which the nets are to be routed.

• Route each net in sequence

• If not all nets can be successfully routed, apply any of a variety of "cleanup" methods, in which selected routings are removed, the order of the remaining nets to be routed is changed, and the remaining routings are attempted again.

This process repeats until all nets are routed or the program (or user) gives up.