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Re: [Nasm-users] Handling timer interrupt
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From: zak100 <zul...@ya...> - 2009-08-09 10:47:18
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Hi,
I have changed the code but still I am getting garbage at kernel startup. I
have got the macro definition at the beginning but the iret code at the end.
I cant understand what ou mean by PIC.
The new code is given below:
;Printing test mesg at kernel startup
;If I move macro at end , i get syntax error.
%macro install 1
push ax
mov ax, 0
mov word[%1*4],isr_add
mov word[%1*4+2],cs
pop ax
%endmacro
mov ax, 7E0H
mov ds,ax
mov es,ax
mov si, msg
mov ah, 0Eh
mov bx, 7
top:
lodsb
cmp al, 0
jz blackhole1
int 10h
jmp short top
blackhole1:install 01ch; calling macro
xor ax,ax; print the mesgA using int10h
mov ds,ax
mov es,ax
mov si,msgA ; "our dear string"
mov bx,7
mov ah,0Eh
msgloop:
lodsb
or al,al
jz end44
int 10h ; since we're still in RM, we can use bios.
jmp msgloop
end44: jmp end44
blackhole:
hlt
jmp blackhole
msg db 'Welcome to the Kernel!', 0
msgA db 'Total minutes elapsed since Kernel start is', 0AH, 0DH
clkcounter db 0
secs db 0
mins db 0
isr_add:
cli
inc byte [byte cs:clkcounter]
cmp byte [byte cs:clkcounter],18; if clkcounter is 18, it means 1 sec
jz handle_secs
sti
iret
handle_secs:
mov byte [byte cs:clkcounter],0
inc byte [byte cs:secs]
cmp byte [byte cs:secs],60;if secs is 60, it means 1 min
jz handle_mins
sti
iret
handle_mins:
mov byte [byte cs:secs],0
inc byte [byte cs:mins]; we are done, now print the number of minutes
elapsed
sti
iret
times 0x200-($-$$) db 0
Kindly somebody plz help me with the above code.
Zulfi.
----------------------------------------------------------
zak100 wrote:
>
> Hi,
> I am trying to handle timer interrupt in a OS like code. I have got a
> bootloader whose code is given below and is working (I am able to see the
> mesg at the start up):
> %define bootseg 0
> %define bootoff 7C00h
>
> %define loadoff 7E00h
>
>
>
>
> ORG 7c00h ;Because BIOS loades the OS at
> ; address 0:7C00h so ORG 7C00h
> ; makes that the refrence to date
> ; are with the right offset (7c00h).
>
>
>
> ; CS = 0 / IP = 7C00h // SS = ? / SP = ?
> ; You are now at address 7c00.
> jmp start ;Here we start the, BIOS gave us now the control.
>
>
>
> ;///////////////////////////////////////////
> ;//Here goes all the data of the program.
> ;///////////////////////////////////////////
>
> xCursor db 0
> yCursor db 0
>
>
> nSector db 0
> nTrack db 0
> nSide db 0
> nDrive db 0
>
> nTrays db 0
>
> ;
> szReady db 'Are You Ready to start Loading the OS...',0
> szErrorReadingDrive db 'Error Reading Drive, Press any Key to
> reboot...',0
> ;//Done Reading a track.
> szPlaceMarker db '~~~~',0
> szDone db 'Done',0
>
> pOS dw loadoff
> ;//Points to where to download the Operating System.
>
> ;/////////////////////////////////
> ;//Here the program starts.
> ;/////////////////////////////////
>
>
> start:
>
> CLI ;Clear Interupt Flag so while setting
> ;up the stack any interrupt would not be fired.
> ;----------------STACK
> mov AX,7B0h ;lets have the stack start at 7c00h-256 = 7B00h
> mov SS,ax ;SS:SP = 7B0h:256 = 7B00h:256
> mov SP,256 ;Lets make the stack 256 bytes.
>
> XOR AX,AX ;Makes AX=0.
> MOV ES,AX ;Make ES=0
> mov DS,ax
>
>
> STI ;Set Back the Interupt Flag after
> ;we finished setting a stack frame.
>
> Call ClearScreen ;ClearScreen()
> LEA AX,[szReady] ;Get Address of szReady.
> CALL PrintMessage ;Call PrintfMessage()
> CALL GetKey ;Call GetKey()
>
> mov bp, 1 ; sectors to load
> CALL DownloadOS
> ; CALL GetKey ;Call GetKey()
> CALL GiveControlToOS ;Give Control To OS.
>
> ;/////////////////////////////////////
> ;//Prints a message to the screen.
> ;/////////////////////////////////////
> PrintMessage:
>
> mov DI,AX ;AX holds the address of the string to Display.
> Mov byte [xCursor],1 ;Column.
>
> ContinuPrinting:
>
> cmp byte [DI],0 ;Did we get to the End of String.
> JE EndPrintingMessage ;if you get to the end of the string
> return.
>
> mov AH,2 ;Move Cursor
> mov DH,[yCursor] ;row.
> mov DL,[xCursor] ;column.
> mov BH,0 ;page number.
> INT 10h
> INC byte [xCursor]
>
> mov AH,0Ah ;Display Character Function.
> mov AL,[DI] ;character to display.
> mov BH,0 ;page number.
> mov CX,1 ;number of times to write character
> INT 10h
>
> INC DI ;Go to next character.
>
> JMP ContinuPrinting ;go to Print Next Character.
>
> EndPrintingMessage:
>
> Inc byte [yCursor] ;So Next time the message would
> ;be printed in the second line.
>
> cmp byte [yCursor],25
> JNE dontMoveCorsurToBegin
> Mov byte [yCursor],0
>
> dontMoveCorsurToBegin:
> ret
>
>
> ;PrintMessage EndP
> ;//////////////////////////////////////
> ;//Waits for the user to press a key.
> ;//////////////////////////////////////
> GetKey: ; PROC
>
> mov ah,0
> int 16h ;Wait for a key press.
> Ret
>
> ;///////////////////////////////////////////
> ;//Gives Control To Second Part Loader.
> ;///////////////////////////////////////////
> GiveControlToOS:
>
> LEA AX,[szDone]
> Call PrintMessage
> CALL GetKey
>
> jmp 7E0h:40h
>
> mov ax, [loadoff + 18h]
>
> push 7E0h
> push ax
> retf
>
> ;///////////////////////////////////
> ;//Clear Screen.
> ;///////////////////////////////////
> ClearScreen:
>
> mov ax,0600h ;//Scroll All Screen UP to Clear Screen.
> mov bh,07
> mov cx,0
> mov dx,184fh
> int 10h
>
> Mov byte [xCursor],0 ;//Set Cursor Position So next
> ;//write would start in
> ;//the beginning of screen.
> Mov byte [yCursor],0
>
> Ret
>
> ;/////////////////////////////////
> ;//PrintPlaceMarker.
> ;/////////////////////////////////
> PrintPlaceMarker:
>
> LEA AX,[szPlaceMarker]
> CALL PrintMessage ;Call PrintfMessage()
> ; CALL GetKey ;Call GetKey()
> ret
>
> ;///////////////////////////////////
> ;//DownloadOS
> ;///////////////////////////////////
> DownloadOS:
>
> mov byte [nDrive],0
> mov byte [nSide],0
> mov byte [nTrack],0
> mov byte [nSector],1 ; desired sector - 1!
>
> ContinueDownload:
>
> INC byte [nSector] ;Read Next Sector.
> cmp byte [nSector],19 ;Did we get to end of track.
> JNE StayInTrack
>
> CALL PrintPlaceMarker ;Print now '~~~~' so the user would
> ;know that we finished reading a track
> INC byte [nTrack] ;If we get to end of track Move to
> next track.
> mov byte [nSector],1 ;And Read Next Sector.
> CMP byte [nTrack],5 ;Read 5 Tracks (Modify this value
> ;to how much Tracks you want to read).
> JE EndDownloadingOS
>
> StayInTrack:
>
> ;ReadSector();
> Call ReadSector
> dec bp
> jz EndDownloadingOS
>
>
> JMP ContinueDownload
> ;If didn't yet finish Loading OS.
>
> EndDownloadingOS:
>
> ret
>
> ;////////////////////////////////////////
> ;//Read Sector.
> ;////////////////////////////////////////
> ReadSector:
>
> mov byte [nTrays],0
>
> TryAgain:
>
> mov AH,2 ;//Read Function.
> mov AL,1 ;//1 Sector.
> mov CH,[nTrack]
> mov CL,[nSector] ;//Remember: Sectors start with 1, not 0.
> mov DH,[nSide]
> mov DL,[nDrive]
> Mov BX,[pOS] ;//ES:BX points to the address
> ;to were to store the sector.
> INT 13h
>
> jnc EndReadSector
>
> mov AH,0 ;Else Reset Drive . And Try Again...
> INT 13h
> cmp byte [nTrays],3 ;Check if you tryed reading
> ;more then 3 times.
>
> JE DisplayError ; if tryed 3 Times Display Error.
>
> INC byte [nTrays]
>
> jmp TryAgain ;Try Reading again.
>
> DisplayError:
> LEA AX,[szErrorReadingDrive]
> Call PrintMessage
> Call GetKey
> mov AH,0 ;Reboot Computer.
> INT 19h
>
>
> EndReadSector:
> ADD WORD [pOS],512 ;//Move the pointer
> ;(ES:BX = ES:pOS = 0:pOS) 512 bytes.
> ;//Here you set the varible
> ;pOS (pOS points to were BIOS
> ;//Would load the Next Sector).
> Ret
>
> ;////////////////////////////////////
> ;//
> ;////////////////////////////////////
>
> times 510 - ($ - $$) db 0
> db 55h, 0AAh
> ;-------------------
>
>
>
> An then I have a kernel code which includes a file also:
>
> %include "lib.inc"
> mov ax, 7E0H
> mov ds,ax
> mov es,ax
> mov si, msg
>
> mov ah, 0Eh
> mov bx, 7
> top:
> lodsb
> cmp al, 0
> jz blackhole1
> int 10h
> jmp short top
>
> blackhole1:install 6
>
> blackhole:
> hlt
> jmp blackhole
>
> msg db 'Welcome to the Kernel!', 0
> msgA db 'Total minutes elapsed since Kernel start is', 0AH, 0DH
> clkcounter db 0
> secs db 0
> mins db 0
>
> times 0x200-($-$$) db 0
>
>
> The include file is given below:
>
> %macro install 1
> push ax
> mov al,%1
> mov ah, 0eh
> int 10h
> pop ax
> ;push ds
> ;mov ax, 0
> ;mov word[%1*4],isr_add
> ;mov word[%1*4+2],cs
> ;pop ds
> %endmacro
>
> isr_add:
> cli
> inc byte [byte cs:clkcounter]
> cmp byte [byte cs:clkcounter],18
> jz handle_secs
> sti
> iret
> handle_secs:
> mov byte [byte cs:clkcounter],0
> inc byte [byte cs:secs]
> cmp byte [byte cs:secs],60
> jz handle_mins
> sti
> iret
> handle_mins:
> mov byte [byte cs:secs],0
> inc byte [byte cs:mins]
> push ds
> push es
>
> xor ax,ax
> mov ds,ax
> mov es,ax
> ; should probably set up a sane stack here, too.
> mov si,msgA ; "our dear string"
>
> ;mov bx,7
> mov ah,0Eh
> msgloop:
> lodsb
> or al,al
> jz end44
> int 10h ; since we're still in RM, we can use bios.
> jmp msgloop
> end44: pop es
> pop ds
> sti
> iret
> sti
> iret
>
> For compilation I am using following commands:
> nasm -f bin bootmz.asm -o boot.bin
>
> nasm -f obj test_k.asm
>
>
>
> alink -oEXE test_k.obj
>
>
> copy /b boot.bin+test_k.exe image.bin
> partcopy image.bin 0 323 -f0
>
> Can somebody plz help me with this?
>
> Zulfi.
>
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