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why can't i use vesa mode ?
Posted: Wed Dec 27, 2006 3:01 am
by mohammed
i used mode 13h to draw
Code: Select all
.model tiny
.data
x dw 0
y dw 0
color db 1
.code
start:
mov ax,0013h
int 10h
mov di, 0a000h
mov es,di
lop:mov ax, 320
mul [Y]
mov di, ax
add di, [X]
mov al, [Color]
stosb
inc y
inc x
inc color
jmp lop
end start
i tried to use the vesa by change the value of ax to 4f02h but it didn't work why ?
Posted: Wed Dec 27, 2006 4:30 am
by Combuster
From the VBE spec:
Code: Select all
Function 02h - Set VBE Mode
Input: AX = 4F02h Set VBE Mode
BX = Desired Mode to set
D0-D8 = Mode number
D9-D10= Reserved (must be 0)
D11 = 0 Use current default refresh rate
= 1 Use user specified CRTC values for refresh rate
D12-13 Reserved for VBE/AF (must be 0)
D14 = 0 Use windowed frame buffer model
= 1 Use linear/flat frame buffer model
D15 = 0 Clear display memory
= 1 Don't clear display memory
ES:DI = Pointer to CRTCInfoBlock structure
Output: AX = VBE Return Status
Note: All other registers are preserved.
i.e. by just changing ax to 4f02, you haven't chosen a mode yet. you'll need to supply the mode number in BX for it to work.
Posted: Wed Dec 27, 2006 5:27 am
by Ready4Dis
Deleted info, was incorrect.
Posted: Wed Dec 27, 2006 8:35 am
by mohammed
Yes, and the location you need to draw to is changed as well, it will no longer be 0xa000, you have to ask the video card what location the video memory is located in.
no it realy worked when i changed the value of bx as Combuster said to the mode wich i wanted but it didn't draw the same !!
http://www.monstersoft.com/tutorial1/VESA_intro.html
all the tutorials availabe put the code with gcc and i have problems with it no one have a complete code in assembly ?
it is so slow in assembling and linking and working!!!
why ?!!!
Posted: Wed Dec 27, 2006 12:15 pm
by Dex
Try this simple demo (for fasm)
Code: Select all
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; ;;
;; fasm example.By Craig Bamford (Dex) 2002. ;;
;; 640*480 8bpp (256 colors) vesa1 ;;
;; C:\fasm vesa1.asm vesa1.com ;;
;; ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
ORG 100h
Start:
mov ax,4f02h
mov bx,101h
int 10h
mov dx,0xa000
mov es,dx
call window
StartAgain:
xor dx,dx
mov [color],0
MainLoop:
push dx
call window
xor bx,bx
inc [color]
mov al,[color]
call static
pop dx
cmp dx,4
je StartAgain
inc dx ;<** here is box number
mov ah,01h
int 16h
jz MainLoop
mov ah,00h
int 16h
mov ax,0003h
int 10h
ret
window:
mov ax,4f05h
mov bx,0
int 10h
xor bx,bx
ret
static:
stosb
inc bx
cmp bx,0x00000
jne static
ret
color db 0
Row db 0
Posted: Wed Dec 27, 2006 2:44 pm
by mohammed
thanks dex
i want you to see my program and told me if this is a high color or my eye cheating me ?
Code: Select all
.model tiny
.data
x dw 0
y dw 0
color db 156
.code
start:
mov ax,4f02h
mov bx,100h
int 10h
mov di, 0a000h
mov es,di
lop:mov ax, 320
mul [Y]
mov di, ax
add di, [X]
mov al, [Color]
stosb
inc y
inc x
jmp lop
end start
Posted: Wed Dec 27, 2006 8:13 pm
by Dex
First you are trying to draw to screen like its one big buff like mode 13h, you can not do this as vesa1 uses banks, which means the screen is div into 64k chucks.
If you take my example screen size and times it = 307200 thata a bit more than 64k
So you write 64k to 0a000h than you switch to the next bank, that what this does:
Code: Select all
window:
mov ax,4f05h
mov bx,0
int 10h
xor bx,bx
ret
Note whats in DX on call this function, is the bank we want, starting with bank 0 ( in the above case we need 5 banks to fill screen ).
Once we swich bank we write another 64k to 0a000h and so on.
Something like this:
As your in realmode you limted to 64k, so this mode uses 1 boxs 64k in size, you need to swich boxs eg:
********box0****
64k
********box1****
64k
********box2****
64k
********box3****
64k
********box4****
64k
****************
Posted: Thu Dec 28, 2006 1:39 am
by mohammed
now i understand why the color just fill the above 1/5 of the screen
thank you
