Optimal bus coding for OR-chained buses

Abstract

This letter presents a novel bus coding technique suitable for a bus with OR chaining that requires data parking at the end of data transmission. Based on the fact that the data parking state is known a priori, the proposed technique encodes the last sequential data value by jointly considering two switching activities, one that occurred due to a change in valid data values and the other that will be subsequently occurred by data parking. Compared to the conventional bus coding scheme that picks a codeword that minimizes only the former, the proposed technique can achieve >3% additional saving of switching activity in average. Evaluation results based on 22-nm CMOS technology show that the proposed scheme, even with its higher encoding energy, can obtain the lower total energy for >0.59mm bus length in comparison with the conventional data bus invert technique.