GATE-A20 AND CPU RESET CIRCUIT FOR MICROPROCESSOR-BASED SYSTEM

摘要

A computer system (100) includes a chipset (120) which controls the gate-A20 signal and the CPU RESET signal in a conventional manner in response to commands from a system microprocessor (112). The computer system (100) further includes a peripheral controller (230) which is programmed to generate an alternative gate-A20 signal and an alternative CPU RESET signal when the peripheral controller (230) has been commanded do override the corresponding signals form the chipset (120). Two signal selectors (272, 276) controlled by the peripheral controller (230) select either the gate-A20 signal and the CPU RESET signal from the chipset (120) or the alternative gate-A20 and the alternative CPU RESET signal for the peripheral controller (230) as respective outputs to control operations of the computer system (100). The use of the alternative signals permits certain operations of the computer system (100) to be directly controlled by an application program without being intercepted by the operating system.