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Int 31 Fn 0302 P - DPMI 0.9+ - Call Real Mode Procedure With Iret Frame [E]
AX = 0302h
BH = flags
bit 0: reset the interrupt controller and A20 line (DPMI 0.9)
reserved, must be 0 (DPMI 1.0+)
others must be 0
CX = number of words to copy from protected mode to real mode stack
ES:(E)DI = selector:offset of real mode call structure
(see INT 31/AX=0300h)
Return: CF clear if successful
real mode call structure modified (all fields except SS:SP, CS:IP
filled with return values from real mode interrupt)
CF set on error
AX = error code (DPMI 1.0+) (8012h,8013h,8014h,8021h)(see AX=0000h)
protected mode stack unchanged
Notes: 16-bit programs use ES:DI as pointer, 32-bit programs use ES:EDI
the flags in the call structure are pushed on the real mode stack to
form an interrupt stack frame, and the trace and interrupt flags are
clear on entry to the handler
the real mode procedure must exit with an IRET
DPMI will provide a small (30 words) real mode stack if SS:SP is zero
the real mode handler must return with the stack in the same state as
it was on being called
See Also: AX=0300h
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