US Patent 7308058 Transparent multi-mode PAM interface

Provided are a method and apparatus for high-speed, multi-mode PAM symbol transmission. A multi-mode PAM output driver drives one or more symbols, the number of levels used in the PAM modulation of the one or more symbols depending on the state of a PAM mode signal. Additionally, the one or more symbols are driven at a symbol rate, the symbol rate selected in accordance with the PAM mode signal so that a data rate of the driven symbols is constant with respect to changes in the state of the PAM mode signal. Further provided are methods for determining the optimal number of PAM levels for symbol transmission and reception in a given physical environment.