Abstract: A pulse amplitude modulated (PAM) mapper includes a constellation matrix memory which stores indications of a plurality of different constellations, wherein at least one of the different stored constellations is of different dimension than another of the stored constellations. The constellations are used individually or together to support a plurality of different modem data rates. In a preferred embodiment, the mapper also includes a logic block, a constellation controller, a PAM code generation block, and an output register. The logic block receives incoming bits and groups the bits as a function of the desired or agreed upon bit rate as indicated by the constellation controller, and provides a plurality of each group of bits to the PAM code generation block, and one or more sign bits to the output register. The PAM code generation block uses the provided bits to choose at least one point from one of the constellations, and uses each chosen constellation point to generate a PAM code (typically .mu.