Embedded Transition Inversion Coding With Low Switching Activity for Serial Links

Serial link interconnection has been proposed for its advantages of reducing crosstalk and area. However, serializing parallel buses tends to increase bit transition and power dissipation. Several coding schemes, such as serial followed by encoding (SE) and transition inversion coding (TIC), have been proposed to reduce bit transition. TIC is capable of decreasing transitions by 15% compared to the SE scheme, but an extra indication bit is added in every data word to represent inversion occurrence. The extra bit increases the transmission overhead and the bit transitions. This paper proposes an embedded transition inversion (ETI) coding scheme that uses the phase difference between the clock and data in the transmitted serial data to tackle the problem of the extra indication bit. The ETI coding scheme reduces the transition by up to 31% compared to SE scheme. The analysis and simulation results indicate that the proposed coding scheme produces a low bit transition for different kinds of data patterns. Using the optimum degree of multiplexing, width, and spacing, the ETI coding scheme achieves 30%-60% energy reduction compared with the parallel bus without overhead. Taking circuit overhead into consideration, the power saving is up to 31.71% and 26.46% at a clock cycle of 250 ps for the 90- and 130-nm CMOS technology for m=2 where m is the number of parallel wires multiplexed into a serial link.