Method and apparatus for protecting flash memory

Abstract

In a computer system including a processor, a system memory, a flash memory, and a memory controller, memory address/window detector coupled to the processor, the memory controller, a first input of a OR logic gate and a first input of an AND gate. The OR logic gate has an output coupled to the memory controller and a second input for receiving a system memory access enable signal. Also included is a memory window control coupled to the system memory, the memory controller, the flash memory, the memory address/window detector, an output of a NOT logic gate and a first input of another AND logic gate. The additional AND logic gate has a second input for receiving a flash memory programming enable signal. A system memory access enable register is included and is coupled to an output of the first AND logic gate, a second input of the OR logic gate, and an input of the NOT logic gate. The memory window control is only accessible when the system memory access enable register is set to disabled. A flash memory programming enable register is included where it is coupled to an output of the additional AND logic gate. Also included is a flash memory programming circuit that is coupled to the flash memory programming enable register and the flash memory. The flash memory programming enable register is disabled if said system memory access enable register is enabled.