这个都是过去DOS时代的汇编源码，虽然已经过去了，但是对于学习汇编还是有帮助的，汇编语言只是程序员一门基础语言，大多人掌握即可，不一定要深入研究.......
comment *
SERTYPE.ASM
Purpose:
Determines the type of UART in each serial port
Author:
Douglas Boling, in PcMag. With some modifications by Yousuf Khan.
*
dosseg
bdseg segment at 40h ;bios data segment
com1 dw ?
com2 dw ?
com3 dw ?
com4 dw ?
ends
_data segment para 'data'
uart1 db 0
uart2 db 0
uart3 db 0
uart4 db 0
portmsg db "COMx: $"
x8250 db "NS 8250 (non-FIFO)",13,10,"$"
x16450 db "NS 8250A/16450/16550 (non-FIFO)",13,10,"$"
xfifo db "NS 16550A/Intel 82510 (FIFO)",13,10,"$"
xdma db "IBM type 3 (FIFO/DMA)",13,10,"$"
pas_de_ports db "No serial ports detected",13,10,"$"
ends
_stack segment para stack 'stack'
db 200h dup (?)
ends
cseg segment para 'code'
mov ax, bdseg
mov es, ax ;ES := Bdseg
mov ax, _data
mov ds, ax ;DS := _data
assume cs:cseg, ds:_data, es:bdseg, ss:_stack
xor al, al ;# of serial ports = 0
mov dx, [com1]
cmp dx, 0
je eoproc
inc al ;# of serial ports = 1
push ax
call uartdet
mov [uart1], al ;remember the type of this UART
pop ax
mov dx, [com2]
cmp dx, 0
je eoproc
inc al ;# of serial ports = 2
push ax
call uartdet
mov [uart2], al
pop ax
mov dx, [com3]
cmp dx, 0
je eoproc
inc al ;# of serial ports = 3
push ax
call uartdet
mov [uart3], al
pop ax
mov dx, [com4]
cmp dx, 0
je eoproc
inc al ;# of serial ports = 4
push ax
call uartdet
mov [uart4], al
pop ax
eoproc:
call disp
mov ah, 4ch
int 21h
delay macro
jmp $+2
endm
uartdet proc near
push bx
push cx
mov bx, dx ;save starting i/o addr
add dx, 4 ;point to modem ctrl reg
in al, dx ;disable interrupts
push ax
and al, 11111011b
out dx, al
mov ch, 0 ;assume type 0
mov dx, bx
add dx, 7 ;see if scratch reg exists
mov al, 55h
cli
out dx, al ;write to scratch reg
delay
in al, dx ;read back
cmp al, 55h
jne endudet
mov al, 0AAh
out dx, al ;write to scratch reg
delay
in al, dx ;read back
sti
cmp al, 0AAh
jne endudet
inc ch ;assume type 1
mov dx, bx
add dx, 2 ;point to FIFO ctrl reg
mov al, 7 ;attempt to enable FIFOs
cli
out dx, al
delay
in al, dx ;read interrupt ID reg
sti
and al, 0c0h ;strip all but FIFO bits
jz endudet ;if bits 0, 16450/16550
inc ch ;assume type 2
mov dx, bx
add dx, 8003h ;point to enhanced reg 1
cli
in al, dx
push ax
or al, 01000000b ;enable DMA transmission
out dx, al
push dx
mov dx, bx
add dx, 2
in al, dx
mov cl, al
pop dx ;restore enhanced reg 1
pop ax
out dx, al
sti
and cl, 0c0h ;again mask all but FIFO ID
cmp cl, 40h
jne endudet ;must be type 2 (FIFO)
inc ch ;must be type 3 (DMA)
endudet:
pop ax
mov dx, bx
add dx, 4 ;point to modem ctrl reg
out dx, al ;restore initial condition
xor ax, ax
mov al, ch
mov dx, bx
pop cx
pop bx
ret
uartdet endp
disp proc near
push ax ;save AX
cmp al, 0 ;no serial ports?
je noports
mov bx, offset ds:[uart1] ;offset of UART type field
mov di, offset ds:[portmsg][3] ;offset of 4th char in message
mov cx, 0
mov cl, al ;number of iterations
@l1:
;
;write "COMx: " message substituting "x" for proper comport #
;
mov dl, 4
sub dl, cl
add dl, 30h ;convert to ASCII number
mov [di], dl
lea dx, portmsg
mov ah, 9
int 21h
;
;write the UART type now
;
mov dl, [bx]
cmp dl, 0
jne @t2
lea dx, x8250
mov ah, 9
int 21h
jmp @eot
@t2: cmp dl, 1
jne @t3
lea dx, x16450
mov ah, 9
int 21h
jmp @eot
@t3: cmp dl, 2
jne @t4
lea dx, xfifo
mov ah, 9
int 21h
jmp @eot
@t4: lea dx, xdma
mov ah, 9
int 21h
@eot: inc bx
loop @l1
jmp eoproc2
noports:
lea dx, pas_de_ports
mov ah, 9
int 21h
eoproc2:
pop ax
ret
disp endp
ends
end
; EOF SERTYPE.ASM