From:	"Radek Zajic" <rzajic AT seznam DOT NOSPAM DOT cz>
Newsgroups:	comp.os.msdos.djgpp,comp.lang.asm.x86,alt.lang.asm
Subject:	Re: Buffers
Date:	Sat, 05 Aug 2000 00:12:11 GMT
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You should take a look at the DPMI functions at INT 0x31 in RB's IntList.
Below is a snippet of RB's IntList release 61: DPMI function Simulate RM
interrupt.
This is the (only?) way how to call real-mode interrupts from protected mode
under DMPI.

I hope it helps.

--
Radek Zajic

rzajic AT seznam DOT NOSPAM DOT cz
(to e-mail me, remove ".NOSPAM" from my e-mail address)

--------E-310300-----------------------------
INT 31 P - DPMI 0.9+ - SIMULATE REAL MODE INTERRUPT
 AX = 0300h
 BL = interrupt number
 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 #03148)
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 #03143)
 protected mode stack unchanged
Notes: 16-bit programs use ES:DI as pointer, 32-bit programs use ES:EDI
 CS:IP in the real mode call structure is ignored for this call,
   instead, the indicated interrupt vector is used for the address
 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
 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
SeeAlso: AX=0302h,AX=FF01h,INT 21/AX=2511h,INT 21/AH=E3h"OS/286"
SeeAlso: INT 2C/AX=0026h,INT 2F/AX=FB42h/BX=000Dh

Format of DPMI real mode call structure:
Offset Size Description (Table 03148)
 00h DWORD EDI
 04h DWORD ESI
 08h DWORD EBP
 0Ch DWORD reserved (00h)
 10h DWORD EBX
 14h DWORD EDX
 18h DWORD ECX
 1Ch DWORD EAX
 20h WORD flags
 22h WORD ES
 24h WORD DS
 26h WORD FS
 28h WORD GS
 2Ah WORD IP
 2Ch WORD CS
 2Eh WORD SP
 30h WORD SS

 

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