Patent ID: 7593468

Claim:
A method of interfacing a high speed signal, comprising: receiving a series of digital signals from a transmitter in response to a clock signal; coding into a Gray code at least once the received digital signals based on a K-L level pulse amplitude modulation (PAM) system in response to the clock signal, wherein K and L are natural numbers and K≠L, and wherein the K-L level PAM system alternately uses a K-level PAM and an L-level PAM, wherein K is 8 and L is 4, and wherein the 4-level PAM has a lowest level corresponding to a third lowest level of the 8-level PAM, and a highest level corresponding to a third highest level of the 8-level PAM; and transferring the coded digital signals to a receiver, wherein coding the received digital signals includes: coding an N-th digital signal among the series of digital signals based on the K-level PAM in response to the clock signal, wherein N is an integer; and coding an N+1-th digital signal among the series of digital signals based on the L-level PAM in response to the clock signal.