DOS下读取spd信息的汇编程序（通过SMBus）

汇编程序编写的读取spd信息的代码：

 ;-----------------------------------------------------------
 ;功能: 通过SMbus 读取内存的SPD 信息
 ;时间: 2015/09
 ;环境: DOS + MASM5
 ;说明: 代码中涉及的smbus规范是基于Intel平台
 ;---------------------------------------------------------
 ;功能: 显示ascii 表示的字符
 echoch macro ascii
     mov ah,
     mov dl,ascii
     int 21h
     endm
 ;---------------------------------------------------------
     .386P
 ;-------------------- data segment ---------------------------------
 dseg segment use16
     busnum dw 0000h  ;总线号0 - 00FFh
     devnum dw 001fh  ;设备号0 - 001Fh
     funnum dw 0007h  ;功能号0 - 0007h
     regnum dw 00ffh  ;寄存器0 - 00FFh
     ;
     sm_base   dw 0000h ;存放smbus 基地址
     sm_devnum dw 0000h   ;a0/a2/a4/a6
     sm_regnum dw 0000h   ;
     ;
     bufferlen =
     buffer db bufferlen dup() ;存放spd  128-byte的信息
     buffer1 db 'smbus base address :'
     buffer2 db 'device index :'
 dseg ends
 ;-------------------- data segment end ----------------------------------
 ;-------------------- code segment ---------------------------------
 cseg segment use16
     assume cs:cseg, ds:dseg
 start:
     mov ax,dseg
     mov ds,ax
     ;----------------------扫描PCI ---------------------
     mov busnum,0000h
     mov devnum,0000h
     mov funnum,0000h
     mov regnum,0000h
 nextreg:
     call pci_read     ;读取pci 配置空间的前4 个字节
     cmp ax,0ffffh     ;判断设备是否存在
     jz nextfun        ;不存在，跳到下一个fun
     ;
     add regnum,08h    ;读class code
     call pci_read
     and eax,0ffffff00h
     cmp eax,0c050000h ;根据class code 判断SMbus Controller( 0c0500 )
     jz find           ;是SMbus Controller
 nextfun:
     mov regnum,0000h
     inc funnum
     cmp funnum,0007h
     ja nextdev        ;funnum 大于 7,跳到下一个dev
     jmp nextreg
 nextdev:
     mov regnum,0000h
     mov funnum,0000h
     inc devnum
     cmp devnum,001fh
     ja nextbus      ;devnum 大于 1fh，跳到下一个bus
     jmp nextreg
 nextbus:
     mov regnum,0000h
     mov funnum,0000h
     mov devnum,0000h
     inc busnum
     cmp busnum,0005h
     ja notfind        ;busnum 大于5，没找到SMbus Controller --结束
     jmp nextreg

     ;--------------------找到SMbus  Controller-------------------
 find:
     sub regnum,08h
     add regnum,20h  ;SMbus 的基地址在pci 配置空间中的偏移地址
     call pci_read   ;读取SMbus 的基地址
     and ax,0fffeh   ;1111_1111_1111_1110,最后一位1 :表示端口方式
     mov sm_base,ax  ;把基地址保存到sm_base
     ;
     ;-----------------------打印smbus 的基地址------------
     mov dx,offset buffer1
     mov cx,
     mov ah,40h
     int 21h
     ;
     mov ax,sm_base
     shr ax,
     push ax
     shr al,
     call toascii
     echoch al
     pop ax
     call toascii
     echoch al
     ;
     mov ax,sm_base
     push ax
     shr al,
     call toascii
     echoch al
     pop ax
     call toascii
     echoch al
     echoch 0dh  ;换行
         echoch 0ah
     ;--------------------读smbus  设备的SPD ----------------
     mov sm_devnum,00a0h   ;设备a0
     ;
 nextd:
     mov sm_regnum,0000h
     mov dx,offset buffer2
     mov cx,
     mov ah,40h
     int 21h
     ;
     mov ax,sm_devnum
     push ax
     shr al,
     call toascii
     echoch al
     pop ax
     call toascii
     echoch al
     echoch ' '
     ;
     call sm_read      ;读128-byte 的spd，存入buffer , 并显示buffer
     echoch 0dh        ;换行
         echoch 0ah
         add sm_devnum,   ;设备号a0/a2/a4/a6
         cmp sm_devnum,0a8h
         jl nextd          ;小于，循环
         ;----------------------------------------
     ;--------------结束，返回DOS -------------
 notfind:
     mov ah,4ch
     int 21h
 ;---------------------------------------------
 ;------------------子程序----------------
 ;----------------------------------------
 ;功能: 通过smbus IO registers 读取spd 信息，并存入buffer
 ;入口:
 ;
 sm_read proc
     push dx
     push ax
     ;
     mov ax,dseg           ;设置目的地址(buffer 的地址)
     mov es,ax             ;段地址为数据段地址
     mov di,offset buffer  ;偏移地址为缓冲区的偏移地址
 nextch:
     ;----------smbus 访问规范--------
     call iodelay
     mov dx,sm_base  ;SMbus 的基地址
     add dx,00h      ;status register
     mov al,0feh     ;
     out dx,al
     call iodelay    ;延时
     ;
     mov dx,sm_base
     add dx,04h       ;slave address register
     mov ax,sm_devnum ;从设备地址:a0/a2/a4/a6  ,
     or al,01h        ;末位:1 - 表示读
     out dx,al
     call iodelay
     ;
     mov dx,sm_base
     add dx,03h       ;command register
     mov ax,sm_regnum ;寄存器索引
     out dx,al
     call iodelay
     inc sm_regnum
     ;
     mov dx,sm_base
     add dx,02h       ;control register
     mov al,48h       ;设置读写模式:字节(48h)、字(4ch)、块(54h)
     out dx,al
     call iodelay
     call iodelay
     ;
     mov dx,sm_base
     add dx,00h
     in al,dx
     cmp al,04h       ;判断读结果
     jz enderr        ;读出错,设备不存在,返回
     ;
     mov dx,sm_base
     add dx,05h      ;data0 register
     in al,dx        ;回读数据
     mov es:[di],al  ;数据保存到buffer 中
     inc di
     cmp sm_regnum,7fh
     ja endsm        ;128-byte  读完
     jmp nextch
 endsm:                    ;读完结束，打印buffer 后，结束
     call print_buffer
     pop ax
     pop dx
     ret
 enderr:                 ;读出错结束，直接退出
     pop ax
     pop dx
     ret
 sm_read endp
 ;--------------------------------------------------
 ;功能:延时,等待外设把数据准备好
 ;
 iodelay proc
     push cx
     mov cx,0ffffh
 delay:
     loop delay
     mov cx,0ffffh
 delay1:
     loop delay1
     pop cx
     ret
 iodelay    endp
 ;---------------------------------------------
 ;功能: 根据eax中的地址读取pci的配置空间,并存入eax
 ;入口: busnum、devnum、funnum、regnum
 ;出口: eax
 ;
 pci_read proc
     ;protect register
     push ebx
     push dx
     ;clear
     xor eax,eax
     xor ebx,ebx
     ;enable
     add eax,1h
     shl eax,
     ;bus number
     mov ebx,ds:[]
     and ebx,0ffh
     shl ebx,
     add eax,ebx
     ;device number
     xor ebx,ebx
     mov ebx,ds:[]
     and ebx,0ffh
     shl ebx,
     add eax,ebx
     ;function number
     xor ebx,ebx
     mov ebx,ds:[]
     and ebx,0ffh
     shl ebx,
     add eax,ebx
     ;register
     xor ebx,ebx
     mov ebx,ds:[]
     and ebx,0ffh
     add eax,ebx
     ;read IO
     mov dx,0cf8h
     out dx,eax
     mov dx,0cfch
     in eax,dx
     ;resume register
     pop dx
     pop ebx
     ret
 pci_read endp
 ;----------------------------------------------
 ;功能:打印buffer的内容(以ascii 形式)
 ;
 print_buffer proc
     push ax
     push ds
     push si
     push cx
     push bp
     ;
     mov ax,dseg      ;设置源地址(buffer 的地址)
     mov ds,ax
     mov si,offset buffer
         mov cx,bufferlen
         cld
 nextline3:
     dec cx
         echoch 0dh
         echoch 0ah
         mov bp,
 nextch3:
     lodsb            ;加载一个字节到al
     ;
     push ax
     shr al,
     call toascii
     echoch al
     pop ax
     call toascii
     echoch al
     echoch ' '
     ;
     dec bp
         jz nextline3
     loop nextch3
     ;
     pop bp     ;出栈顺序与入栈顺序相反
     pop cx
     pop si
     pop ds
     pop ax
     ret
 print_buffer endp
 ;----------------------------------------
 ;功能:把al 的低4位转成ascii码,并存入al
 ;入口: al
 ;出口: al
 toascii proc
     and al,0fh  ;高四位清零
     add al,90h  ;1001_xxxx
     daa
     adc al,40h
     daa
     ret
 toascii endp
 ;-------------------------------------------
 cseg ends
 ;------------- code segment end --------------------------
     end start