 An alternate approach, used in many microprocessors, is to use PLAs or ROMs (instead of combinational logic) mainly for instruction decoding, and let a simple state machine (without much, or any, microcode) do most of the sequencing.The MOS Technology 6502 is an example of a microprocessor using a PLA for instruction decode and sequencing.The PLA is visible in photomicrographs of the chip, and its operation can be seen in the transistor-level simulation.