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Elimination of Bracket Straddle in Bracket Type Printed Circuit Wiring Programs

IP.com Disclosure Number: IPCOM000085832D
Original Publication Date: 1976-Jun-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 20K

Publishing Venue

IBM

Related People

Backer, PO: AUTHOR [+4]

Abstract

The problem of automatic wire routing on multilayered cards and boards is often solved by a type of computer program called bracket wiring. This routing method introduces a special kind of interference between connecting paths called bracket straddle. Described is a general method for managing bracket straddle during the global wiring phase; which is a preliminary phase of wiring concerned with reducing interference of every kind. The Problem.

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Elimination of Bracket Straddle in Bracket Type Printed Circuit Wiring Programs

The problem of automatic wire routing on multilayered cards and boards is often solved by a type of computer program called bracket wiring. This routing method introduces a special kind of interference between connecting paths called bracket straddle. Described is a general method for managing bracket straddle during the global wiring phase; which is a preliminary phase of wiring concerned with reducing interference of every kind. The Problem.

Cards and boards used in computer manufacture have fixed geometries in which their pins and the feedthrough via holes form a rectangular array of nodes. The space between two adjacent rows is a channel with capacity for routing a number of printed wires. A bracket is a wire which connects two nodes of the same row and passes entirely in one of the channels on either side of that row. In bracket wiring, every connecting path is a sequence of brackets. Two brackets straddle if they lie in the same row and their entry and exit nodes alternate, as do the brackets A and B in the figure. Two such brackets must be assigned to opposite channels, otherwise they interfere, and one of them must fail. Three brackets which straddle each other in pairs cannot be assigned to the same plane.

The global phase of wiring selects for each connection out of the total number of possible paths some number of projected, or potential paths. The goal of the selection is to reduce mutual interference of paths. The result of this phase may be just one path for every connection, or a number of alternate paths sequenced in order of preference. The type of interference which leads to congestion of resources has yielded to load and capacity analysis. Bracket straddle requires a different approach.

Suppose that paths are chosen by global wiring on the basis of congestion analysis, and consist of brackets, where however, no bracket has yet been assigned to a channel. This set of paths is now given to the straddle algorithm with the following task:

Produce as large a subset of these paths as possible, with bracke...