Logically Determined Design: Clockless System Design with NULL Convention Logic

APPENDIX C

Pipeline Simulation

The space-time diagrams used in Chapters 10 and 11 were generated by a Microsoft Excel [34] spreadsheet that simulates the behavior of the pipeline and produces space-time diagrams of the flow of successive wavefronts through successive pipeline cycles. The simulation models the forward propagation of data path wavefronts through the pipeline as well as the backward propagation of acknowledge signals through the pipeline. Although an acknowledge signal moves backward in the pipeline space, it progresses forward in time. So the signal relationships of multiple-pipeline stages can be arranged such that all signal relationships are progressive in time and thus expressible as a spreadsheet simulation. A pipeline ring, on the other hand, entails a circular reference and cannot be directly modeled by a spreadsheet simulation.

The delay for all component paths of the 13 cycles of the simulation can be individually set in a delay data table that drives the simulation, as shown in Figure C.1. Note that the vertical axis represents successive wavefronts entering the pipeline. The horizontal axis represents successive cycle components of the pipeline. The table details each delay associated for each wavefront at each pipeline registration stage. The column ‘reg ...