All 9S12 devices have on-chip Flash and RAM, and are intended primarily for single-chip mode operation. However, a multiplexed address/data bus supports expanded mode operation for some applications. Sometimes external RAM is used to emulate internal Flash during code development, so that program loading is faster, and the debugger can set unlimited breakpoints in the program in RAM.

There are several 9S12 families available. Products utilizing the 9S12C, 9S12D, 9S12E, and 9S12NE families are currently offered by Technological Arts. 9S12C is a low-cost consumer part, with on-chip CAN subsystem, 9S12D has multiple CAN channels, 9S12E has IrDA and DAC subsystems, and 9S12NE has a complete PHY/MAC on-chip, for easy implementation of 100-BaseT networks. New products are being added frequently.