Semi-detailed bus routing with variation reduction

Abstract

A bus routing algorithm is presented which not only minimizes wire length but also selects the bits in the bus to avoid twisting and conflicts. The resulting bus routes are regular, thus having strong immunity to variations. Minimization for wire length/delay differences between different bits is also implemented.

A simultaneous bus orientation and bused pin flipping algorithm

“…Various bus routing algorithms [11,3,9] including ours can be plugged in to the floorplanner to handle buses. The cost function used in the simulated annealing was…”

“…A type of interlocking, two turning nodes being connected by a short edge, was discussed in [9]. The concept of interlocking will be extended in the next definition.…”

“…Since a routing node can have at most 4 incident edges and a group node's degree is also limited by some constant number, the complexity can be written as O(|D|). This is much more efficient than enumerating all combinations of bused pin flipping and then running an algorithm like [9] for each bus. Under certain circumstances, we may not want the algorithm to fail immediately after a conflict is detected.…”

“…The simplified bus routing estimation techniques used in the floorplanning [1][2][3][4]6,7] make the routability and the bus routing quality of the final floorplan in doubt. Recently, a semi-detailed bus routing algorithm was proposed [9], which reported good quality and efficiency. This single bus routing algorithm focuses on the turning points in the virtual net and determines their orientations.…”

“…Our algorithm, as opposed to the single bus router reported in [9], handles the routing of multiple buses and bused pin flipping at the same time. The algorithm can be used in the following scenarios: (1) as a standalone program that works on a given floorplan to handle all the buses; (2) as a bus routing procedure being frequently called during bus centric floorplanning; (3) as part of a full router to handle buses and bused pin flipping.…”