Differential operation oriented multiple-valued encoding and circuit realization for asynchronous data transfer

This paper presents an asynchronous data transfer scheme using 2-color 2-phase dual-rail encoding based on a differential operation and its circuit realization. The proposed encoding enables seamless asynchronous data transfer without inserting a spacer, because each logic value is represented by two kinds of codewords with dual-rail, called "color" data. Since the difference x - x′ between components of a codeword (x, x′) becomes constant in every valid state, the data-arrival state can be detected by calculating the difference x - x′. From the viewpoint of circuit implementation, during the state transition, since the dual-rail x and x′ are denned so as to transit differentially, the compatibility with a comparator using a differential amplifier becomes high, which results in reduction of the cycle time. It is evaluated using HSPICE simulation with a 0.18μm CMOS technology that communication speed using the proposed dual-rail encoding becomes 1.4 times faster than that using conventional dual-rail encoding.