a20.asm

操作系统实验教程核心技术与编程实例书中地例子代码

OPEN_A20    PROC    
            PUSH AX
            IN   AL,92H
            OR   AL,2
            OUT  92H,AL
            POP  AX
            RET
OPEN_A20    ENDP
CLOSE_A20   PROC    
            PUSH AX
            IN   AL,92H
            AND  AL,0FDH
            OUT  92H,AL
            POP  AX
            RET
CLOSE_A20   ENDP