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PORTIO.ASM
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Assembly Source File
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1993-07-16
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5KB
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138 lines
; ******************************************************************
; <portio.asm> code file
;
; Function definitions for port access routines
; inp(port) - read single byte from I/O port
; inpw(port) - read single word from I/O port pair
; outp(port) - write single byte to I/O port
; outpw(port) - write single word to I/O port pair
;
; For IBM C Set/2 Version 1.0
;
; DISCLAIMER:
; -------------------------
; This code and the accompanying documentation is hereby placed in
; the public domain. It is not part of any standard product and
; is provided solely as an example for your private and/or
; commercial use. You may freely use or distribute this code in
; derived works as long as you do not attempt to prevent others
; from doing likewise. Neither the author, nor his employer,
; shall be liable for any damages arising from your use of this
; code; it is provided solely ASIS with no warranty whatsoever.
;
; Author contact: Michael Thompson
; tommy@msc.cornell.edu
; ******************************************************************
;
; Register use modified 7/16/93 by Mike Warot (ka9dgx@chinet.com)
;
P@IOCODE segment 'CODE'
assume cs:P@IOCODE
;=============================================================================
; These routines must be declared as
;
; unsigned short _Far16 _Fastcall inp(unsigned short port);
; unsigned short _Far16 _Fastcall inpw(unsigned short port);
; unsigned short _Far16 _Fastcall outp(unsigned short, unsigned short);
; unsigned short _Far16 _Fastcall outpw(unsigned short, unsigned short);
;
; in the CSET/2 declarations. The fastcall convention passes the values on
; the registers AX, DX as assumed below. The short return allows use of AX
; only on exit. This should be nearly at the limit of the 32->16 call
; convention.
;
; Compiling and linkage requires these routines to be stored in a DLL so are
; 16 bit. I could make them 32 bit IF I could get a true protected mode 32
; bit assembler. Microsoft maybe there, but I refuse to buy their toys
; anymore.
;
; General make process:
; masm /Mx portio;
; link /map /noi /nod portio,portio.dll,,,portio.def
; implib portio.lib portio.def
;
; portio.def must contain
; LIBRARY PORTIO
; DESCRIPTION 'Dynamically-linked Run-Time Library for Port Access'
; PROTMODE
; CODE PRELOAD EXECUTEONLY IOPL
;
; EXPORTS
; @inp
; @outp
; @inpw
; @outpw
;
; The CODE IOPL is required - all CODE segments are give IOPL priveleges.
; For some reason, can't figure out how to override one MASM segment.
; @ indicates a fastcall routine apparently, /Mx preserves case.
;=============================================================================
;=============================================================================
; Subroutine to output byte to specified port
;
; Usage: unsigned short = outp (unsigned short port, unsigned short byte)
; unsigned short = outpw(unsigned short port, unsigned short word)
;
; Inputs: DX - port
; AX - contains value to be sent (low byte only for outp)
;
; Output: AX - byte value sent
;=============================================================================
@outp proc far
public @outp
assume ds:nothing,es:nothing
;
out dx,al ; And send one byte
xor ah,ah ; Say didn't send hi
ret
;
@outp endp
@outpw proc far
public @outpw
assume ds:nothing,es:nothing
;
out dx,ax ; And send one byte
ret
;
@outpw endp
;=============================================================================
; Subroutine to read input from a specified port
;
; Usage: unsigned short = inp (unsigned short port)
; unsigned short = inpw(unsigned short port)
;
; Inputs: DX - port
;
; Output: AX - byte (word) value received
;=============================================================================
@inp proc far
public @inp
assume ds:nothing,es:nothing
;
in al,dx ; Read the byte
xor ah,ah ; Clear AH
ret
;
@inp endp
@inpw proc far
public @inpw
assume ds:nothing,es:nothing
;
in ax,dx ; Read the word
ret
;
@inpw endp
P@IOCODE ends
;
end