OP的文字：
如何在 NASM 汇编中制作一个向后计时器 3 分钟？
计时器不倒转。
编辑：
看起来
split modelap mode要制作倒计时器，我们可以编写类似于
changeTime但是我们应该使用
sub 55 msadd 55 ms控制：
空格键 - 启动计时器/快照
左移 - 分割模式
右移 - 圈数模式
r - 重置计时器
代码：
[org 0x0100]
jmp start
;---------------------------------------;
hrs: dw 0 ; split mode data
min: dw 0 ;
s: dw 0 ;
ms: dw 0 ;
lhrs: dw 0 ; lap mode data
lmin: dw 0 ;
ls: dw 0 ;
lms: dw 0 ;
oldkb: dd 0 ; old vector
sMode: db 0 ; split mode
lMode: db 0 ; lap mode
startTimer: db 0 ; timer on/off
snapshot: db 0 ; capture time
lapTime: db 0 ; lapTime on/off
location: db 6 ; display data starting from line 6
;---------------------------------------;
clrscr:
pusha ;
push es ;
mov ax, 0xB800 ; ax = B800
mov es, ax ; es = B800
xor di, di ; di = 0000
mov ax, 0x720 ; ax = 0720, ' ' + attrib 0x07
mov cx, 2000 ; cx = 2000
cld ; clear DF, add di,2
rep stosw ; es:di = ax
pop es ;
popa ;
ret ;
;---------------------------------------;
printLayout:
pusha ;
push es ;
mov ax, 0xB800 ; ax = B800
mov es, ax ; es = B800
mov di, 160 ; di = 0xAE
mov byte[es:di+0], ' ' ; write to video mem
mov byte[es:di+2], 'H' ;
mov byte[es:di+4], 'R' ;
mov byte[es:di+6], 'S' ;
mov byte[es:di+10], ':' ;
mov byte[es:di+14], 'M' ;
mov byte[es:di+16], 'I' ;
mov byte[es:di+18], 'N' ;
mov byte[es:di+22], ':' ;
mov byte[es:di+26], 'S' ;
mov byte[es:di+28], 'E' ;
mov byte[es:di+30], 'C' ;
mov byte[es:di+34], ':' ;
mov byte[es:di+38], 'M' ;
mov byte[es:di+40], 'L' ;
mov byte[es:di+42], 'S' ;
pop es ;
popa ;
ret ;
;---------------------------------------;
kbisr: ; new keyboard interrupt, stay resident
push ax ;
in al, 0x60 ; read from port 0x60, output buffer
cmp al, 147 ; 'r' key, reset timer , 0x93 - 0x80 = 0x13
jz reset ; reset timer
jnz modChanger ; change mode, split/lap
reset:
mov word [cs:hrs], 0 ; reset split data
mov word [cs:min], 0 ;
mov word [cs:s], 0 ;
mov word [cs:ms], 0 ;
mov word [cs:lhrs], 0 ; reset lap data
mov word [cs:lmin], 0 ;
mov word [cs:ls], 0 ;
mov word [cs:lms], 0 ;
call clrscr ; clear screen
mov byte [cs:location], 6 ; line 6, show split/lap time on this line if space bar is hit
jmp EOI1 ; end of interrupt 1
modChanger: ; switch between lap and split mode
cmp al, 170 ; left shift, 0xaa - 0x80 = 0x2a
jnz checkLMode1 ; activate lap mode
; activate split mode
mov byte [cs:lMode], 0 ; lap mode = 0, deactivate lap mode
cmp byte [cs:sMode], 1 ; if split mode = 1, already active?
jz EOI1 ; end of interrupt 1
mov byte [cs:sMode], 1 ; else activate split mode = 1
jmp EOI1 ;
checkLMode1: ; lap mode
cmp al, 182 ; right shift, 0xb6 - 0x80 = 0x36
jnz startTime ; start timer
mov byte [cs:sMode], 0 ; split mode = 0
cmp byte [cs:lMode], 1 ; if lap mode = 1, already active?
jz EOI1 ; end of interrupt 1
mov byte [cs:lMode], 1 ; lap mode = 1
jmp EOI1
;---------------------------------------;
startTime:
cmp al, 185 ; space bar, 0xB9 - 0x80 = 0x39
jnz oldKbHandler ; no, use old keyboard procedure
; yes, start the timer
cmp byte [cs:startTimer], 1 ; is the timer activated?
jz check0 ; yes
; no
mov byte [cs:startTimer], 1 ; turn the timer on
check0:
cmp byte [cs:sMode], 1 ; if split mode = 1
jnz check1 ; no
; yes
mov byte [cs:snapshot], 1 ; snapshot = 1, total time from start
jmp EOI1 ; end of interrupt 1
check1:
cmp byte [cs:lMode], 1 ; if lap mode = 1
jnz EOI1
mov byte [cs:lapTime], 1 ; lapTime = 1, each lap time
jmp EOI1
EOI1:
mov al, 0x20 ; send the signal to the 8259A controller
out 0x20,al ; end of the interrupt
pop ax ;
iret ;
oldKbHandler:
pop ax ;
jmp far [cs:oldkb] ; old keyboard handler code
;---------------------------------------;
;---------------------------------------;
printstr:
push bp ;
mov bp, sp ;
pusha ;
push es ;
mov ax, 0xb800 ; ax = b800
mov es, ax ; es = b800
mov di, [bp+4] ; di = 482, video mem offset
mov ax, [bp+6] ; ax = hrs
mov bx, 10 ; bx = 000a
mov cx, 0 ; cx = 0000
nextdigit:
mov dx, 0 ; dx = 0000
div bx ; dx:ax = 0000:hrs
add dl, 0x30 ; ascii digit
push dx ;
inc cx ; cx = 0001
cmp ax, 0 ;
jnz nextdigit ;
cmp cx, 1 ;
jnz nextpos
mov byte [es:di], '0' ; print '0' at curret position
add di, 2 ; next position
nextpos:
pop dx
mov dh, 0x07 ; color
mov [es:di], dx ;
add di, 2 ;
loop nextpos ;
pop es ;
popa ;
pop bp ;
ret 4 ;
;---------------------------------------;
printTime:
push bp ;
mov bp, sp ;
pusha ;
push es ;
mov ax, 0xB800 ; ax = b800
mov es, ax ; es = b800
mov di, [bp+4] ; di = 490
; print hours
push word [bp+6] ; [bp+6] = hrs
add di, 2 ; di = 492
push di ;
call printstr ;
; print colon
add di, 8 ; di = 500
mov byte [es:di], ':' ;
; print minutes
push word [bp+8] ; [bp+8] = mins
add di, 4 ; di = 504
push di ;
call printstr ;
; print colon
add di, 8 ; di = 512
mov byte [es:di], ':' ;
; print seconds
push word [bp+10] ; [bp+10] = secs
add di, 4 ; di = 516
push di ;
call printstr ;
; print colon
add di, 8 ; di = 524
mov byte [es:di], ':' ;
; print miliseconds
push word [bp+12] ; [bp+12] = milisecs
add di, 4 ; di = 528
push di ;
call printstr ;
pop es ;
popa ;
pop bp ;
ret 10 ;
;---------------------------------------;
stopWatch:
pusha
push es
call printLayout ; print " HRS : MIN : SEC : MLS "
; print " COUNTDOWN TIMER"
; print starting data
; save on the stack
push word [cs:ms] ; miliseconds
push word [cs:s] ; seconds
push word [cs:min] ; minutes
push word [cs:hrs] ; hours
push 480 ; video mem offset, line 3
call printTime ;
cmp byte [cs:startTimer], 1 ;
jnz dEOI ; end of interrupt
changeTime:
add word [cs:ms], 55 ; add 55 miliseconds
cmp word [cs:ms], 1000 ; if 1000 miliseconds
jle modCheck ;
mov word [cs:ms], 0 ; reset miliseconds
inc word [cs:s] ; +1 second
cmp word [cs:s], 60 ; if 60 seconds
jnz modCheck ;
mov word [cs:s], 0 ; reset seconds
inc word [cs:min] ; +1 minute
cmp word [cs:min], 60 ; if 60 minutes
jnz modCheck ;
mov word [cs:min], 0 ; reset minutes
inc word[cs:hrs] ; +1 hour
jmp modCheck ;
modCheck:
cmp byte [cs:sMode], 1 ; split mode
jz splitMode
cmp byte [cs:lMode], 1 ; lap mode
jz lapMode
jmp EOI
dEOI:
jmp EOI
;---------------------------------------;
;---------------------------------------;
splitMode:
cmp byte [cs:snapshot], 1 ; is snapshot on?
jnz eEOI ;
mov byte [cs:snapshot], 0 ; deactivate snapshot
push word [cs:ms] ; save on the stack
push word [cs:s] ;
push word [cs:min] ;
push word [cs:hrs] ;
; position calculation
mov al, 80 ; calculate new cursor position
mul byte [cs:location] ;
shl ax, 1 ;
add byte [cs:location], 2 ; used in calculation of the new offset
push ax ;
call printTime ;
eEOI:
jmp EOI
;eEOI: jmp EOI
;---------------------------------------;
;---------------------------------------;
lapMode:
cmp byte [cs:lapTime], 1 ;
jnz xEOI ;
mov byte [cs:lapTime], 0 ;
mov ax, [cs:ms] ;
mov bx, [cs:s] ;
mov cx, [cs:min] ;
mov dx, [cs:hrs] ;
l1:
sub ax, [cs:lms] ;
cmp ax, 0 ;
jge l2 ;
add ax, 1000 ;
dec bx ;
l2:
mov [cs:lms],ax ;
sub bx, [cs:ls] ;
cmp bx, 0 ;
jge l3 ;
add bx, 60 ;
dec cx ;
l3:
mov [cs:ls],bx ;
jmp l4 ;
xEOI:
jmp EOI ;
l4:
sub cx, [cs:lmin] ;
cmp cx, 0 ;
jge l5 ;
add cx, 60 ;
dec dx ;
l5:
mov [cs:lmin],cx ;
sub dx, [cs:lhrs] ;
mov [cs:lhrs],dx ;
push word [cs:lms] ;
push word [cs:ls] ;
push word [cs:lmin] ;
push word [cs:lhrs] ;
;Position Calculation
mov al, 80 ;
mul byte [cs:location] ;
shl ax, 1 ;
add byte [cs:location], 2 ;
push ax ;
call printTime ;
jmp EOI ;
EOI:
mov al, 0x20 ;
out 0x20, al ;
return:
pop es ;
popa ;
iret ;
;---------------------------------------;
start:
mov ax, 0 ; ax = 0000
mov es, ax ; es = 0000
mov ax, [es:9*4] ; int 09h, keyboard int offset
mov [oldkb],ax ; ds:[oldkb] = xxxx
mov ax, [es:9*4+2] ; int 09h, keyboard int segment
mov [oldkb+2], ax ; ds:[oldkb+2] = xxxx
call clrscr ; clear screen
cli ; clear IF
mov word [es:9*4], kbisr ; new int 09h procedure, offset
mov [es:9*4+2], cs ; and segment
; no save ? old off:seg
mov word [es:8*4], stopWatch ; new int 08h (timer), offset
mov [es:8*4+2], cs ; and segment, executed every 55 ms, 18.2 times per sec
sti ; set IF
mov dx, start ; dx = allocate memory,size(in bytes) = start offset
; dx = number of 16 bytes paragraphs
add dx, 16 ; include PSP (256 bytes = 16 paragraphs x 16 bytes)
mov cl, 4 ;
shr dx, cl ; dx = (total bytes / 16 bytes) = paragraphs number
mov ax, 0x3100 ; terminate and stay resident
int 21h ; DOS int
我添加了 5 个变量，其中包含倒数计时器的当前状态。 OP 想要 3 分钟，所以就这样了。
chrs: dw 0 ; countdown timer data
cmin: dw 3 ;
csec: dw 0 ;
cms: dw 0 ;
cdt: db 0 ; countdown timer on/off
键 c 添加到键盘处理程序
kbisr注：
我认为单圈时间代码无法正常工作。我没深究过。
代码：
[org 0x0100]
jmp start
;---------------------------------------;
hrs: dw 0 ; split mode data
min: dw 0 ;
s: dw 0 ;
ms: dw 0 ;
lhrs: dw 0 ; lap mode data
lmin: dw 0 ;
ls: dw 0 ;
lms: dw 0 ;
oldkb: dd 0 ; old vector
sMode: db 0 ; split mode
lMode: db 0 ; lap mode
startTimer: db 0 ; timer on/off
snapshot: db 0 ; capture time
lapTime: db 0 ; lapTime on/off
location: db 6 ; display data starting from line 6
; *** countdown timer code
; hardcoded values
; add own procedure if you want
; to take data from a user
chrs: dw 0 ; countdown timer data
cmin: dw 3 ;
csec: dw 0 ;
cms: dw 0 ;
cdt: db 0 ; countdown timer on/off
;---------------------------------------;
clrscr:
pusha ;
push es ;
mov ax, 0xB800 ; ax = B800
mov es, ax ; es = B800
xor di, di ; di = 0000
mov ax, 0x720 ; ax = 0720, ' ' + attrib 0x07
mov cx, 2000 ; cx = 2000
cld ; clear DF, add di,2
rep stosw ; es:di = ax
pop es ;
popa ;
ret ;
;---------------------------------------;
printLayout:
pusha ;
push es ;
mov ax, 0xB800 ; ax = B800
mov es, ax ; es = B800
mov di, 174 ; di = 0xAE
mov byte[es:di+0], ' ' ; write to video mem
mov byte[es:di+2], 'H' ;
mov byte[es:di+4], 'R' ;
mov byte[es:di+6], 'S' ;
mov byte[es:di+10], ':' ;
mov byte[es:di+14], 'M' ;
mov byte[es:di+16], 'I' ;
mov byte[es:di+18], 'N' ;
mov byte[es:di+22], ':' ;
mov byte[es:di+26], 'S' ;
mov byte[es:di+28], 'E' ;
mov byte[es:di+30], 'C' ;
mov byte[es:di+34], ':' ;
mov byte[es:di+38], 'M' ;
mov byte[es:di+40], 'L' ;
mov byte[es:di+42], 'S' ;
; *** countdown timer code
mov di, 260 ;
mov byte[es:di], 'C' ;
mov byte[es:di+2], 'O' ;
mov byte[es:di+4], 'U' ;
mov byte[es:di+6], 'N' ;
mov byte[es:di+8], 'T' ;
mov byte[es:di+10], 'D' ;
mov byte[es:di+12], 'O' ;
mov byte[es:di+14], 'W' ;
mov byte[es:di+16], 'N' ;
mov byte[es:di+18], ' ' ;
mov byte[es:di+20], 'T' ;
mov byte[es:di+22], 'I' ;
mov byte[es:di+24], 'M' ;
mov byte[es:di+26], 'E' ;
mov byte[es:di+28], 'R' ;
pop es ;
popa ;
ret ;
;---------------------------------------;
kbisr: ; new keyboard interrupt, stay resident
push ax ;
in al, 0x60 ; read from port 0x60, output buffer
cmp al, 147 ; 'r' key, reset timer , 0x93 - 0x80 = 0x13
jz reset ; reset timer
; *** countdown timer code
cmp al, 174 ; 'c' key, reset countdown timer, 0xAE - 0x80 = 0x2E
jz countdown
jnz modChanger ; change mode, split/lap
; *** countdown timer code
countdown:
; cmp byte [cs:cdt], 2 ; cdt already reached zero?
; jz cdt_reset
cmp byte[cs:cdt], 1 ; is cdt activated?
jz cdt_stop
inc byte[cs:cdt] ; start cdt
jmp EOI1 ; end of interrupt 1
cdt_stop:
dec byte [cs:cdt] ; stop cdt
jmp EOI1 ;
;cdt_reset:
; dec byte [cs:cdt]
; jmp EOI1
reset:
mov word [cs:hrs], 0 ;
mov word [cs:min], 0 ;
mov word [cs:s], 0 ;
mov word [cs:ms], 0 ;
; reset the lap time
mov word [cs:lhrs], 0 ;
mov word [cs:lmin], 0 ;
mov word [cs:ls], 0 ;
mov word [cs:lms], 0 ;
call clrscr ; clear screen
mov byte [cs:location], 6 ; line 6 , show split/lap time on this line if spacebar is hit
jmp EOI1 ; end of interrupt 1
modChanger: ; switch between lap and split mode
cmp al, 170 ; left shift, 0xaa - 0x80 = 0x2a
jnz checkLMode1 ; activate lap mode
; activate split mode
mov byte [cs:lMode], 0 ; lap mode = 0, deactivate lap mode
cmp byte [cs:sMode], 1 ; if split mode = 1, already active?
jz EOI1 ; end of interrupt 1
mov byte [cs:sMode], 1 ; else activate split mode = 1
jmp EOI1 ;
checkLMode1: ; lap mode
cmp al, 182 ; right shift, 0xb6 - 0x80 = 0x36
jnz startTime ; start timer
mov byte [cs:sMode], 0 ; split mode = 0
cmp byte [cs:lMode], 1 ; if lap mode = 1, already active?
jz EOI1 ; end of interrupt 1
mov byte [cs:lMode], 1 ; lap mode = 1
jmp EOI1
;---------------------------------------;
startTime:
cmp al, 185 ; space bar, 0xB9 - 0x80 = 0x39
jnz oldKbHandler ; no, use old keyboard procedure
; yes, start the timer
cmp byte [cs:startTimer], 1 ; is the timer activated?
jz check0 ; yes
; no
mov byte [cs:startTimer], 1 ; turn the timer on
check0:
cmp byte [cs:sMode], 1 ; if split mode = 1
jnz check1 ; no
; yes
mov byte [cs:snapshot], 1 ; snapshot = 1, total time from start
jmp EOI1 ; end of interrupt 1
check1:
cmp byte [cs:lMode], 1 ; if lap mode = 1
jnz EOI1
mov byte [cs:lapTime], 1 ; lapTime = 1, each lap time
jmp EOI1
EOI1:
mov al, 0x20 ; send the signal to the 8259A controller
out 0x20,al ; end of the interrupt
pop ax ;
iret ;
oldKbHandler:
pop ax ;
jmp far [cs:oldkb] ; old keyboard handler code
;---------------------------------------;
;---------------------------------------;
printstr:
push bp ;
mov bp, sp ;
pusha ;
push es ;
mov ax, 0xb800 ; ax = b800
mov es, ax ; es = b800
mov di, [bp+4] ; di = 482, video mem offset
mov ax, [bp+6] ; ax = hrs
mov bx, 10 ; bx = 000a
mov cx, 0 ; cx = 0000
nextdigit:
mov dx, 0 ; dx = 0000
div bx ; dx:ax = 0000:hrs
add dl, 0x30 ; ascii digit
push dx ;
inc cx ; cx = 0001
cmp ax, 0 ;
jnz nextdigit ;
cmp cx, 1 ;
jnz nextpos
mov byte [es:di], '0' ; print '0' at curret position
add di, 2 ; next position
nextpos:
pop dx
mov dh, 0x07 ; color
mov [es:di], dx ;
add di, 2 ;
loop nextpos ;
pop es ;
popa ;
pop bp ;
ret 4 ;
;---------------------------------------;
printTime:
push bp ;
mov bp, sp ;
pusha ;
push es ;
mov ax, 0xB800 ; ax = b800
mov es, ax ; es = b800
mov di, [bp+4] ; di = 490
; print hours
push word [bp+6] ; [bp+6] = hrs
add di, 2 ; di = 492
push di ;
call printstr ;
; print colon
add di, 8 ; di = 500
mov byte [es:di], ':' ;
; print minutes
push word [bp+8] ; [bp+8] = mins
add di, 4 ; di = 504
push di ;
call printstr ;
; print colon
add di, 8 ; di = 512
mov byte [es:di], ':' ;
; print seconds
push word [bp+10] ; [bp+10] = secs
add di, 4 ; di = 516
push di ;
call printstr ;
; print colon
add di, 8 ; di = 524
mov byte [es:di], ':' ;
; print miliseconds
push word [bp+12] ; [bp+12] = milisecs
add di, 4 ; di = 528
push di ;
call printstr ;
pop es ;
popa ;
pop bp ;
ret 10 ;
;---------------------------------------;
stopWatch:
pusha
push es
call printLayout ; print " HRS : MIN : SEC : MLS "
; print " COUNTDOWN TIMER"
; print starting data
; save on the stack
push word [cs:ms] ; miliseconds
push word [cs:s] ; seconds
push word [cs:min] ; minutes
push word [cs:hrs] ; hours
push 494 ; video mem offset, line 3
call printTime ;
;cmp byte [cs:startTimer], 1
;jnz dEOI ; end of interrupt
;*** countdown timer code
push word [cs:cms] ; miliseconds
push word [cs:csec] ; seconds
push word [cs:cmin] ; minutes
push word [cs:chrs] ; hours
push 578 ; video mem offset, line 3
call printTime ;
cmp byte [cs:startTimer], 1 ; is the timer activated?
jnz dEOI ; no, end of interrupt
cdtimer:
pusha
cmp byte [cs:cdt], 1 ; is cdt active?
jnz cdt_deactivated ;
mov ax, [cs:cms] ;
mov bx, [cs:csec] ;
mov cx, [cs:cmin] ;
mov dx, [cs:chrs] ;
sub ax, 55 ;
cmp ax, 0 ;
jge cdt_secs ; if ms = [0 - 999]
; < 0, dec secs, adjust ms
xor si,si ; check if cdt reached zero
add si,dx ;
add si,cx ;
add si,bx ;
cmp si,0 ;
jz cdt_zero ; countdown finished
add ax, 1000 ; adjust ms
sub bx, 1 ; dec secs
cdt_secs:
mov [cs:cms], ax ; ms after calculation
cmp bx, 0
jge cdt_mins ; if sec = [0 - 59]
; < 0, dec mins, adjust secs
add bx, 60 ;
sub cx, 1 ;
cdt_mins:
mov [cs:csec], bx ; secs after calculation
cmp cx, 0 ;
jge cdt_hrs ; if mins = [0 - 59]
; < 0, dec hrs, adjust mins
add cx, 60 ;
sub dx, 1 ;
cdt_hrs:
mov [cs:cmin], cx ; mins after calculations
cmp dx, 0 ;
jge cdt_done ; if hrs = [0 - 23]
; < 0, adjust hrs
add dx, 24 ; x
cdt_done:
mov [cs:chrs], dx ; hrs after calculation
jmp cdt_deactivated
cdt_zero:
mov byte [cs:cms], 0 ; all done, restart cdt
mov byte [cs:csec], 0 ;
mov byte [cs:cmin], 3 ;
mov byte [cs:chrs], 0 ;
mov byte [cs:cdt], 0 ; stop cdt
cdt_deactivated:
popa
;---------------------------------------;
changeTime:
add word [cs:ms], 55 ; add 55 miliseconds
cmp word [cs:ms], 1000 ; if 1000 miliseconds
jle modCheck ;
mov word [cs:ms], 0 ; reset miliseconds
inc word [cs:s] ; +1 second
cmp word [cs:s], 60 ; if 60 seconds
jnz modCheck ;
mov word [cs:s], 0 ; reset seconds
inc word [cs:min] ; +1 minute
cmp word [cs:min], 60 ; if 60 minutes
jnz modCheck ;
mov word [cs:min], 0 ; reset minutes
inc word[cs:hrs] ; +1 hour
jmp modCheck ;
modCheck:
cmp byte [cs:sMode], 1 ; split mode
jz splitMode
cmp byte [cs:lMode], 1 ; lap mode
jz lapMode
jmp EOI
dEOI:
jmp EOI
;---------------------------------------;
;---------------------------------------;
splitMode:
cmp byte [cs:snapshot], 1 ; is snapshot on?
jnz eEOI ;
mov byte [cs:snapshot], 0 ; deactivate snapshot
push word [cs:ms] ; save on the stack
push word [cs:s] ;
push word [cs:min] ;
push word [cs:hrs] ;
; position calculation
mov al, 80 ; calculate new cursor position
mul byte [cs:location] ;
shl ax, 1 ;
add ax, 4 ;
mov si,0xb800 ;
mov es,si ;
mov si, ax ; split mode id location
mov byte [es:si], 'S' ; split mode id
add ax,10 ;
add byte [cs:location], 2 ; new line number
push ax ;
call printTime ;
eEOI:
jmp EOI
;eEOI: jmp EOI
;---------------------------------------;
;---------------------------------------;
lapMode:
cmp byte [cs:lapTime], 1 ; is lap time activated?
jnz xEOI ; no, end of interrupt
; yes
mov byte [cs:lapTime], 0 ; deactivate lap time
mov ax, [cs:ms] ; move current values to regs
mov bx, [cs:s] ;
mov cx, [cs:min] ;
mov dx, [cs:hrs] ;
; Test:
; 03:04:04:500 - lap 1 - same as split mode
; 06:13:00:200 - lap 2 - 03:09:55:700
;
l1:
sub ax, [cs:lms] ; 500-0=500 | 200-500=-300
cmp ax, 0 ;
jge l2
add ax, 1000 ; | -300+1000=700 |
dec bx ; | 0-1=-1 |
cmp bx,0 ;
jb secs_59 ;
secs_59:
mov bx,59 ; seconds, top of the range [0-59]
l2:
mov [cs:lms],ax ; 500 | 700
sub bx, [cs:ls] ; 4-0=4 | 59-4=55 |
cmp bx, 0 ;
jge l3 ;
add bx, 60 ;
dec cx ;
cmp cx,0 ;
jb mins_59 ;
mins_59:
mov cx,59 ;
l3:
mov [cs:ls],bx ; 4 | 55 |
jmp l4
xEOI:
jmp EOI
l4:
sub cx, [cs:lmin] ; 4-0=4 | 13-4=9 |
cmp cx, 0 ;
jge l5
add cx, 60
dec dx
cmp dx,0
jb hours_59
hours_59:
mov dx,59 ; hours, top of the range [0-59]
l5:
mov [cs:lmin],cx ; 4 | 9 |
sub dx, [cs:lhrs] ; 3-0=3 | 6-3=3|
mov [cs:lhrs],dx ; 3 | 3 |
push word [cs:lms] ; value after each lap
push word [cs:ls]
push word [cs:lmin]
push word [cs:lhrs]
; position calculation
mov al, 80 ; calculate new cursor position
mul byte [cs:location] ;
shl ax, 1 ;
add ax, 4 ;
mov si,0xb800 ;
mov es,si ;
mov si, ax ; lap mode id location
mov byte [es:si], 'L' ; lap mode id
add ax,10 ;
add byte [cs:location], 2 ; new line number
push ax ;
call printTime ;
jmp EOI
EOI: ; EOI - End of Interrupt
mov al, 0x20 ;
out 0x20, al ;
return:
pop es ;
popa ;
iret ;
;---------------------------------------;
start:
mov ax, 0 ; ax = 0000
mov es, ax ; es = 0000
mov ax, [es:9*4] ; int 09h, keyboard int offset
mov [oldkb],ax ; ds:[oldkb] = xxxx
mov ax, [es:9*4+2] ; int 09h, keyboard int segment
mov [oldkb+2], ax ; ds:[oldkb+2] = xxxx
call clrscr ; clear screen
cli ; clear IF
mov word [es:9*4], kbisr ; new int 09h procedure, offset
mov [es:9*4+2], cs ; and segment
; no save ? old off:seg
mov word [es:8*4], stopWatch ; new int 08h (timer), offset
mov [es:8*4+2], cs ; and segment, executed every 55 ms, 18.2 times per sec
sti ; set IF
mov dx, start ; dx = allocate memory,size(in bytes) = start offset
; dx = number of 16 bytes paragraphs
add dx, 16 ; include PSP (256 bytes = 16 paragraphs x 16 bytes)
mov cl, 4 ;
shr dx, cl ; dx = (total bytes / 16 bytes) = paragraphs number
mov ax, 0x3100 ; terminate and stay resident
int 21h ; DOS int