A channel router is a specific variety of router for integrated circuits. Normally using two layers of

interconnect In telecommunications, interconnection is the physical linking of a carrier's network with equipment or facilities not belonging to that network. The term may refer to a connection between a carrier's facilities and the equipment belonging to ...

, it must connect the specified

pins A pin is a device used for fastening objects or material together. Pin or PIN may also refer to: Computers and technology * Personal identification number (PIN), to access a secured system ** PIN pad, a PIN entry device * PIN, a former Dutch de ...

on the top and bottom of the channel. Specified nets must also be brought out to the left and right of the channel, but may be brought out in any order. The height of the channel is not specified - the router computes what height is needed. The ''

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...

'' of a channel, defined for every ''x'' within the channel, is the number of nets that appear on both the left and right of a vertical line at that ''x''. The maximum density is a lower bound on the height of the channel. A "cyclic constraint" occurs when two

occur in the same column (but with different orders) in at least two columns. In the example shown, nets 1 and 3 suffer from cyclic constraints. This can only be solved by "doglegs" as shown on net 1 of the example. Channel routers were one of the first forms of routers for

integrated circuits An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...

, and were heavily used for many years, with YACR perhaps the best known program. However, modern

chips ''CHiPs'' is an American crime drama television series created by Rick Rosner and originally aired on NBC from September 15, 1977, to May 1, 1983. It follows the lives of two motorcycle officers of the California Highway Patrol (CHP). The serie ...

have many more than 2 interconnect layers. Although the effort was made to extend channel routers to more layers,Fang, S., Feng, W., and Lee, S. 1992. . In Proceedings of the 29th ACM/IEEE Conference on Design Automation (Anaheim, California, United States, June 08–12, 1992). Annual ACM IEEE Design Automation Conference. IEEE Computer Society Press, Los Alamitos, CA, 579-584 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 router Area is the quantity that expresses the extent of a region on the plane or on a curved surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while ''surface area'' refers to the area of an open su ...

s have in general taken over.

References

{{reflist Digital electronics Autorouters