Int 31 Fn 0201  P - Dpmi 0.9+ - Set Real Mode Interrupt Vector             [E]

   AX = 0201h
   BL = interrupt number
   CX:DX = segment:offset of real mode handler

Return: CF clear

Note:  all memory that may be touched by a hardware interrupt handler must be
     locked down with INT 31/AX=0600h

See Also: AX=0200h,AX=0205h,AX=0600h,INT 21/AX=2505h