Int 15H Function 89H
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Description: Enter Protected Mode [AT] [PS/2]
Switches the CPU from real mode into protected mode.
Input Output
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AH=89H If function successful
BH=interrupt number for IRQ0, (CPU is in protected mode)
written to ICW2 of 8259 PIC #1 Carry flag=clear
(must be evenly divisible by 8, AH=00H
determines IRQ0-IRQ7) CS=user-defined selector
BL=interrupt number for IRQ8, DS=user-defined selector
written to ICW2 of 8259 PIC #2 ES=user-defined selector
(must be evenly divisible by 8, SS=user-defined selector
determines IRQ8-IRQ15) If function unsuccessful
ES:SI=segment:offset of Global (CPU is in real mode)
Descriptor Table (GDT) Carry flag=set
AH=FFH
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