Programmable logic system for filtering commands to a microprocessor

摘要

A system utilizes one or more programmable logic arrays or gate arrays for regulating the commands available to a microprocessor, and intercepting certain of those commands according to predetermined criteria. The system selects and processes designated commands relating to the FORCE-A20 signal and CPU-RESET signal for a keyboard controller functionally attached to an INTEL 80286 or 80386 microprocessor. The system includes one or more programmable logic arrays or gate arrays for allowing all input commands to pass directly through to the keyboard controller except the command sequence relating to the FORCE-A20 signal or the CPU-RESET signal.