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: reserved, 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 #2819 at 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 #2814)
   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