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 its ...

, it must connect the specified

pins A pin is a device, typically pointed, used for fastening objects or fabrics together. Pins can have the following sorts of body: *a shaft of a rigid inflexible material meant to be inserted in a slot, groove, or hole (as with pivots, hinges, an ...

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 ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

'' 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 (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...

, 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. After the final first-run telecast on NBC in May 1983, the series went into reruns on Sundays fr ...

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 measure of a region's size on a 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 surface or the boundary of a three-dime ...

s have in general taken over.

References

{{reflist Digital electronics Autorouters