打开或关闭一个或多个键盘 LED 并不是在其中一个 BIOS 变量中写入单个值的简单问题!
它包括输出到几个键盘端口以及更新几个 BIOS 变量,以便 BIOS 和 DOS 仍然可以知道这些指示灯的状态。
下一个程序会执行设置 CapsLock 指示器所需的所有操作。
该程序经过测试,可在 DOS 6.20 等真正的 DOS 下完美运行。
如果程序输出“0”一切顺利,如果您看到“1”,则无法设置指标。
在仿真下会发生什么还有待观察。 DOSBox 例如。更改 CapsLock 条件但拒绝点亮相关 LED。
ORG 256 ;Create .COM program
push ds
mov ax, 0040h ;BIOS data segment
mov ds, ax
mov dl, 00000100b ;Set CapsLock
call SetIndicators ; -> CF
pop ds
mov dl, "0"
adc dl, 0
mov ah, 02h ;Display character
int 21h
mov ah, 01h ;Wait for a key
int 21h
int 20h ;Terminate
; - - - - - - - - - - - - - - - - - - - - - - -
; IN (dl) OUT (CF)
SetIndicators:
test byte ptr [0097h], 01000000b
stc
jnz SetIndicators_3 ;Update in progress -> CF=1
push ax
push cx
push dx
and dl, 00000111b
mov al, dl
mov cl, 4
shl al, cl
and byte ptr [0017h], 10001111b
or [0017h], al
and byte ptr [0097h], 11111000b
or [0097h], dl
mov al, 0EDh ;Command to set KB leds
call SendToPort60
test byte ptr [0097h], 10000000b ;Was command acknowledged ?
jnz SetIndicators_1 ;No
mov al, dl
call SendToPort60
test byte ptr [0097h], 10000000b ;Was command acknowledged ?
jz SetIndicators_2 ;Yes
SetIndicators_1:
mov al, 0F4h ;Command to enable KB
call SendToPort60
SetIndicators_2:
and byte ptr [0097h], 00111111b ;OK -> CF=0
pop dx
pop cx
pop ax
SetIndicators_3:
ret
; - - - - - - - - - - - - - - - - - - - - - - -
; IN (IF=0) OUT ()
WaitForEmptyInbuffer:
push ax
push cx
mov cx, 03E3h
WaitForEmptyInbuffer_1:
in al, 61h
and al, 00010000b ;Toggles each refresh request
cmp al, ah
je WaitForEmptyInbuffer_1
mov ah, al
in al, 64h
test al, 00000010b ;Input buffer is full
loopnz WaitForEmptyInbuffer_1
pop cx
pop ax
ret
; - - - - - - - - - - - - - - - - - - - - - - -
; IN (al,ds=0040h) OUT ()
SendToPort60:
push ax
push bx
push cx
mov bh, al
mov bl, 3
SendToPort60_1:
cli
and byte ptr [0097h], 01001111b
call WaitForEmptyInbuffer
mov al, bh
out 60h, al ;This also enables KB !!!
sti ;STI is essential because FAh/
mov cx, 03E3h ; FEh arrive thru interrupt 9
SendToPort60_2:
test byte ptr [0097h], 00010000b ;Was aknowledged ?
jnz SendToPort60_4 ;Yes
test byte ptr [0097h], 00100000b ;Needs resending ?
jnz SendToPort60_3 ;Yes
in al, 61h
and al, 00010000b ;Toggles each refresh request
cmp al, ah
je SendToPort60_2
mov ah, al
loop SendToPort60_2
SendToPort60_3:
dec bl
jnz SendToPort60_1
or byte ptr [0097h], 10000000b ;Command was NOT aknowledged or
SendToPort60_4:
pop cx ; ... KB kept asking to resend!
pop bx
pop ax
cli
ret
; - - - - - - - - - - - - - - - - - - - - - - -