Scan the keyboard to obtain scan codes

问题:

So I'm learning how to make an OS. The problem is that every website says to scan the keyboard to obtain the scancodes in order to detect input. How do I 'scan' the keyboard? I know this question seems very ridiculous, but I really don't know how to do that, and I need help. I also have to mention that I googled it a lot.

回答1:

Example for polling the keyboard port without using an ISR (x86-CPU):

cli
mov  al, 2               ; dissable IRQ 1
out  21h, al
sti
;---------------------------------------------
AGAIN:
in   al, 64h             ; get status byte 
test al, 1               ; check outputbuffer
jz  short NOKEY
test al, 20h             ; PS2-Mouse byte?
jnz short NOKEY
in   al, 60h             ; get scancode (makecode or breakcode)

; place your code here for comparing.....

NOKEY:
jmp AGAIN
;---------------------------------------------
QUIT:
cli
xor  al, al              ; enable IRQ 1
out  21h, al
sti
;---------------------------------------------
; DATA 
TASTTAB DB 02h,03h,04h,05h,06h,07h,08h,09h,0Ah,0Bh,0Ch,0Dh
        DB 10h,11h,12h,13h,14h,15h,16h,17h,18h,19h,1Ah,1Bh,1Eh,1Fh
        DB 20h,21h,22h,23h,24h,25h,26h,27h,28h,29h,2Bh,2Ch,2Dh,2Eh,2Fh
        DB 30h,31h,32h,33h,34h,35h,39h
        DB 56h
tablen =  ($-TASTTAB)

TEXTTAB DB "1234567890ß'"      ; (using german letters)
        DB "qwertzuiopü+as"
        DB "dfghjklöä^#yxcv"
        DB "bnm,.- "
        DB "<"
textablen  =  ($-TEXTTAB)

Within an ISR simple use "in al, 60h" for to get the scancode.