Logically Determined Design: Clockless System Design with NULL Convention Logic

CHAPTER 5

Cycle Granularity

The cycles of a logically determined system can be any granularity. They can be large or they can be very small. System performance depends on the period it takes a cycle to cycle. Large cycles are slower than small cycles so a critical factor of logically determined system design is the degree to which the size of cycles can be minimized [45,46,47,48]. The cycle period depends on the cycle path shown in Figure 5.1. The cycle path includes the spanning completion detection path, the acknowledge path, the spanning completeness path of the acknowledge signal, and the data path between the spanning acknowledge and the completion detection, which may include a combinational expression. As examples get visually more complex, cycles will be indicated by highlighting the completion/acknowledge path of the cycle, as shown in Figure 5.1.

Smaller cycles can be achieved by partitioning combinational expressions, by partitioning the data path, and by integrating the data path combinational logic and control logic. The smallest possible cycle consists of a single 1 value variable data path with no combinational expression shown in Figure 5.2

Figure 5.1 Cycle path and ...