io.asm

一个小型的操作系统,采用gcc进行开发,几千行的代码,方便初学者学习

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;
; Snixos Project version 1.0, 2003.6
; (C) Copyright 2003,2004,2005 Jockeyson,KeqiangGao <[e-mail]>
; All Rights Reserved.
; Distributed under the terms of the GNU General Public License.

; This program is a free and open source software and you can redistribute 
; it and/or modify it under the terms of the GNU General Public License as
; published by the Free Software Foundation. As no any liability is assumed 
; for any incidental or consequential damages in connection with the 
; information or program fragments contained herein,so any exception arised
; is at your own risk. It is ABSOLUTELY WITHOUT ANY WARRANTY.
; Bug report please send to [e-mail] .
;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;
; io.asm : data transfer through low level I/O port 
; Author : [e-mail], [e-mail]
; Time   : 2003.6 
;

bits 32 
global outb, inb, outb_delay, inb_delay 

; prototype in C: void outb(int value,int port) 
; send value sized in one byte to port
outb:
	push ebp
	mov ebp,esp
	push eax
	push edx
        mov eax,dword [esp+16] ; arg value
        mov edx,dword [esp+20] ; arg port
	out dx,al
	pop edx
	pop eax
	leave
	ret 

; prototype in C:  outb_b(int value,int port) 
; send value sized in one byte to port but with a little more delay
outb_delay:
	push ebp
	mov ebp,esp
	push eax
	push edx
        mov eax,dword [esp+16] ; arg value
        mov edx,dword [esp+20] ; arg port
	out dx,al
	nop
	nop
	nop
	nop
	pop edx
	pop eax
	leave

; prototype in C: unsigned char inb(int port)
; get a byte value from port and return what just got
inb:
	push ebp
	mov ebp,esp
	push edx
	mov edx,[esp+12] ; arg port
	in al,dx         ; return value saved in ax
	pop edx
	leave
	ret

; prototype in C: unsigned char inb_delay(int port)
; get a byte value from port and return what just got, but with a little more delay
inb_delay:
	push ebp
	mov ebp,esp
	push edx
	mov edx,[esp+12] ; arg port
	in al,dx	 ; return value saved in ax
	nop
	nop
	nop
	nop
	pop edx
	leave
	ret