Routing of Analog Busses with Parasitic Symmetry Lars

Routing of Analog Busses with Parasitic Symmetry Lars Schreiner, Markus Olbrich, Erich Barke, Volker Meyer zu Bexten

Contents • • • Motivation Net Bundle Routing Trapezoid Methodology Results Conclusions/Future Work Lars Schreiner: ISPD 2005 2

Contents • • • Motivation Net Bundle Routing Trapezoid Methodology Results Conclusions/Future Work Lars Schreiner: ISPD 2005 3

Motivation • Groups of wires (net bundles) have to be routed symmetrically - Symmetry = equal capacitive coupling and resistance for each wire • Automatic balancing of wire length • Automatic generation of shielding patterns • Automatic generation of slotted/split wires Lars Schreiner: ISPD 2005 4

Example of a Net Bundle with Parasitic Symmetry Lars Schreiner: ISPD 2005 5

Contents • • • Motivation Net Bundle Routing Trapezoid Methodology Results Conclusions/Future Work Lars Schreiner: ISPD 2005 6

Steps of Net Bundle Routing 1 Calculation of virtual terminals and net order Path search for net bundle 2 Routing of the net bundle to the terminals 3 Calculation of wire length differences and adjustment area search 4 Use of Module generator for wire implementation Lars Schreiner: ISPD 2005 7

Basic Procedure T 1 a T 2 a 4 3 2 1 = Virtual Terminal = Terminal T 1 b T 2 b Lars Schreiner: ISPD 2005 8

Separation of Terminal/Net Bundle Routing • Nets are treated and routed together as bundles. • Technology independent module generators can be used. • Problem complexity is reduced. • Keeping symmetry is easier. Lars Schreiner: ISPD 2005 9

Net Ordering During Path Search (1) 1 3 2 2 3 1 virtual terminal • • 3 2 1 BUS-module from Module generator terminal bundle „False“ net order of the right terminal bundle Consideration during path search necessary Lars Schreiner: ISPD 2005 10

Net Ordering During Path Search (2) Possible solution of example 1 3 2 2 3 1 3 2 1 Lars Schreiner: ISPD 2005 11

Contents • • • Motivation Net Bundle Routing Trapezoid Methodology Results Conclusions/Future Work Lars Schreiner: ISPD 2005 12

T- and L-Structures of Trapezoid Methodology = = -45° 0° Generator call: BUS N=3 LENGTH=4 e-5 WIDTH=5 e-6 LAYER=2 BEVELSTART=45 BEVELEND=0 Lars Schreiner: ISPD 2005 13

Benefits of Trapezoid Methodology • Universal use for many geometries - Lines, T- and L-structures are implemented by the same module generator • Technology information hidden in module generator - Router gets only necessary technology information - Shielding and Slotting are hidden in the generator • Easy maintainability and adaptation to new technologies Lars Schreiner: ISPD 2005 14

Adjustment Modules • Shorter wires have to be stretched • Two cases: - Adjustment to the favorable site - Adjustment to the unfavorable site Problem: Bent or terminal connection Solution: Adjustment modules Lars Schreiner: ISPD 2005 15

Examples of Adjustment Modules Lars Schreiner: ISPD 2005 16

Benefits of Adjustment Modules • Wire length balancing is done by module generator. • Different net bundle modules are generated for balancing bents, asymmetries, etc. • Resistive differences are adjusted. • Capacitive balancing is possible. Lars Schreiner: ISPD 2005 17

Contents • • • Motivation Net Bundle Routing Trapezoid Methodology Results Conclusions/Future Work Lars Schreiner: ISPD 2005 18

Hand Made vs. Router Lars Schreiner: ISPD 2005 19

Symmetric Coupling Consideration During Path Search Lars Schreiner: ISPD 2005 20

Contents • • • Motivation Net Bundle Routing Trapezoid Methodology Results Conclusions/Future Work Lars Schreiner: ISPD 2005 21

Conclusion • Routing of net bundles • Consideration of routing constraints - Parallel wires Symmetric capacitive coupling Wire length difference calculation Symmetric terminal connection • Module generators - Trapezoid methodology - Adjustment modules Lars Schreiner: ISPD 2005 22

Future Work • 45° Routing • Twisted wires • Inductances Lars Schreiner: ISPD 2005 23