Coding a terminated bus for low power

Coding was proposed as a general method of decreasing power dissipation for the I/O. Lower power dissipation can be obtained by using extra bus liner for coding the data. This paper presents an application of the general theory of limited-weight codes for a class of parallel terminated buses with pull-up terminators (e.g. Rambus). Power dissipation on such a bus-line is larger for a logical 1 and it follows that patterns with few 1s should be chosen. A perfect k/2-limited weight code equivalent to the previously proposed Bus-Invert method and a novel non-perfect 3-limited weight code are described. Both codes can be algorithmically generated and practical issues related to their implementation on the Rambus are discussed.