outp.asm

C标准库源代码

        page    ,132
        title   outp - output from ports
;***
;outp.asm - _outp, _outpw and _outpd routines
;
;       Copyright (c) 1993-1997, Microsoft Corporation. All rights reserved.
;
;Purpose:
;       Defines the write-to-a-port functions: _outp(), _outpw() and outpd().
;
;*******************************************************************************

        .xlist
        include cruntime.inc
        .list


page
;***
;int            _outp(port, databyte)   - write byte from port
;unsigned short _outpw(port, dataword)  - write word from port
;unsigned long  _outpd(port, datadword) - write dword from port
;
;Purpose:
;       Write single byte/word/dword to the specified port.
;
;Entry:
;       unsigned short port - port to write to
;
;Exit:
;       returns value written.
;
;Uses:
;       EAX, EDX
;
;Exceptions:
;
;*******************************************************************************

        CODESEG

        public _outp, _outpw, _outpd

_outp   proc

        xor     eax,eax
        mov     dx,word ptr [esp + 4]
        mov     al,byte ptr [esp + 8]
        out     dx,al
        ret

_outp   endp


_outpw  proc

        mov     dx,word ptr [esp + 4]
        mov     ax,word ptr [esp + 8]
        out     dx,ax
        ret

_outpw  endp


_outpd  proc

        mov     dx,word ptr [esp + 4]
        mov     eax,[esp + 8]
        out     dx,eax
        ret

_outpd  endp

        end