World Library  
Flag as Inappropriate
Email this Article

Channel router

Article Id: WHEBN0012352696
Reproduction Date:

Title: Channel router  
Author: World Heritage Encyclopedia
Language: English
Subject: Electronic design automation
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Channel router

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

A channel router is a specific variety of router for integrated circuits. Normally using two layers of interconnect, it must connect the specified pins 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.

Figure 2: A solution to the channel routing problem shown above. Solutions are not unique, and this is just one of the many possible.

The density 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 pins 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 ICs,[1] and were heavily used for many years, with YACR[2] perhaps the best known program. However, modern chips have many more than 2 interconnect layers. 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.

References

  1. ^ Feller, A. 1976. Automatic layout of low-cost quick-turnaround random-logic custom LSI devices. In Proceedings of the 13th Conference on Design Automation (San Francisco, California, United States, June 28–30, 1976). DAC '76. ACM Press, New York, NY, 79-85.
  2. ^ Reed, J., Sangiovanni-Vincentelli, A., Santomauro, M.; A New Symbolic Channel Router: YACR2, Computer-Aided Design of Integrated Circuits and Systems, IEEE Transactions on, Vol.4, Iss.3, July 1985 Pages: 208- 219
  3. ^ Braun, D., Burns, J., Davadas, S., Ma, H. K., Mayaram, K., Romeo, F., and Sangiovanni-Vincentelli, A. 1986. Chameleon: a new multi-layer channel router. In Proceedings of the 23rd ACM/IEEE Conference on Design Automation (Las Vegas, Nevada, United States). Annual ACM IEEE Design Automation Conference. IEEE Press, Piscataway, NJ, 495-502.
  4. ^ Fang, S., Feng, W., and Lee, S. 1992. A new efficient approach to multilayer channel routing problem. 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 article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.