Two-dimensional codes for low power

Coding was previously proposed for reducing power consumption in CMOS. The original formulations use extra redundancy in space (number of bus lines) for reducing the bus transition activity (and consequently the dynamic power and simultaneous switching noise). This paper proposes several new coding techniques for low power. First it looks at codes in which redundancy in time is used for reduced bus activity. Two-dimensional codes with redundancy in both time and space can then be developed for extra power reduction. Interestingly, these two-dimensional codes can be unrolled in either space or time in order to obtain new one-dimensional codes in the other dimension. More powerful codes using Run-Length Limited (RLL), phase-modulation and amplitude-modulation techniques are finally proposed.