Logically Determined Design: Clockless System Design with NULL Convention Logic

CHAPTER 14

Complex Pipeline Structures

Complex structures of pipelines can be built by grafting pipelines one at a time onto a growing structure. Each new pipeline graft can be modeled as a two-pipeline structure, with one pipeline being integral to the existing structure and the other pipeline being the one grafted. The pipeline integral to the existing structure will have already been integrated into the structure, and modifying it could corrupt the integrity of the existing structure. So in most cases the integral pipeline will be taken as a static referent pipeline and the pipeline being grafted will be the one that is modified.

14.1 LINEAR FEEDBACK SHIFT REGISTER EXAMPLE

The example will be a fairly complex linear feedback shift register (LFSR). Figure 14.1 shows the model of the LFSR, which is a ring structure with XOR functions crossing through it. The squares are registers initialized to the value indicated. The data flow clockwise around the pipeline ring, with pipelines branching across the ring through the XOR functions resulting in a complex structure of data paths.

Figure 14.1 LFSR model.

The discussion will begin with a mapping of the model into a collapsed data path ...