Acorn Examples

The Acorn GitHub repository contains hundreds of test-cases in the tests directory. Among these cases, the following are especially instructive as examples for your own work.

Name of Acorn Input File (hyperlinked) Description Thumbnail 80n_16mmX16mm_5L_15um_res_minimal_example.txt Four-layer package substrate with 80 nets. This simple case uses default design rules, and contains no differential pairs, pin-swap zones, or high-cost routing zones. It takes only a few minutes to complete on a modern laptop with multiple cores. 80n_16mmX16mm_5L_15um_res_example1.txt Four-layer package substrate with 80 nets, similar to the above case (80n_16mmX16mm_5L_15um_res_minimal_example.txt). However, the current case includes realistic design rules in addition to keep-out zones that define the perimeter of a square package with 8-millimeter sides. Keep-out zones also define the locations of BGA sites, which are visible in the thumbnail at right as large circles. Cost-zones are used to encourage the autorouter to primarily use one layer ('Pkg_M1') for most of the routing. This routing is colored red in the thumbnail image. 80n_16mmX16mm_5L_15um_res_example2.txt Four-layer package substrate with 80 nets, similar to the above case (80n_16mmX16mm_5L_15um_res_example1.txt). However, the current case includes four nets that are part of differential pairs. These are visible in the upper-right corner of the thumbnail to the right. One of these pairs is defined as P/N-swappable, which allows the autorouter to avoid the type of wire-crossing that's visible in the other differential pair. Finally, this design includes net-specific design rules, resulting in wider traces for selected nets. This case takes approximately a half hour to complete on a modern laptop with multiple cores. 80n_16mmX16mm_6L_15um_res_example3.txt Four-layer package substrate with 80 nets, similar to the above case (80n_16mmX16mm_5L_15um_res_example2.txt). However, the current case includes two PCB layers and ring-shaped 'swap-zones' on both of these layers. Because all the nets' terminals are located in this circular swap-zone (yellow circular ring, in the thumbnail at right), this case acts as an escape-routing exercise, in which Acorn attempts to optimize the BGA map and PCB routing to route the nets from the die through the package and beyond the shadow of the package on the PCB. This case illustrates the use of design-rule zones to limit the routing in certain regions. The case further uses design-rule zones to restrict the directions of traces to 45° angles on the PCB layers. This case takes approximately 3 hours to complete on a modern laptop with multiple cores.