Channel router

Normally using two layers of interconnect, it must connect the specified pins on the top and bottom of the channel.

The maximum density is a lower bound on the height of the channel.

In the example shown, nets 1 and 3 suffer from cyclic constraints.

Although the effort was made to extend channel routers to more layers,[3][4] this approach was never very popular, since it did not work well with over-the-cell routing where pins are not movable.

In recent years, area routers have in general taken over.

Figure 1: A channel routing problem. The numbered pins on the top and bottom of the channel must be connected. The nets specified on the left and right of the channel must be brought to that end of the channel
Figure 2: A solution to the channel routing problem shown above. Solutions are not unique, and this is just one of the many possible.