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Problem with printing
Posted: Tue Feb 08, 2005 2:48 pm
by beyondsociety
Ive been brushing up on my assembly language skills and I am in the process of trying to get a character to print multiple times as though it looks like its loading.
I can print the character a certain number of times, but it gets displayed all at once. Any help or tips would be appreciated.
This is what I have so far, two different versions. Ive even tryed adding a loop but couldnt get it to work.
Code: Select all
; Print dots
mov ah, 0x09 ; AH = write character function
mov al, '.' ; AL = character to display
mov bx, 0x0007 ; BH = video page number, BL = attribute
mov cx, 0x0010 ; CX = number of times to write character
int 0x10 ; Bios video function
; Print a character using the video memory
mov ax, 0x0b800 ; Segment of video buffer in real mode
mov es, ax ; Put this into es
xor di, di ; Clear di, ES:DI points to video memory
mov ah, 4 ; Attribute - red
mov al, "G" ; Character to put there
mov cx, 1 ; Amount of times to put it there
cld ; Direction - forwards
rep stosw ; Output character at ES:[DI]
Thanks in advance.
Re:Problem with printing
Posted: Tue Feb 08, 2005 4:52 pm
by mystran
If you want them to print one at a time, then you obviously need to wait between printing the characters.
Re:Problem with printing
Posted: Tue Feb 08, 2005 8:03 pm
by Dex4u
Yes as mystran said it needs a delay, this code in nasm, Works for none critical delay, 70 = 1 second.
Code: Select all
BITS 16
ORG 100h
SECTION .text
START:
xor ah,ah
int 16h
mov word[count],0
ddf:
call FullVertWait
cmp word [count],70
jne ddf
;Do some thing in here
xor ah, ah
int 16h
ret
;**************************
FullVertWait:
MOV DX,3DAh
Vr:
IN AL,DX
TEST AL,8
JNZ Vr ;wait until Verticle Retrace starts
Nvr:
IN AL,DX
TEST AL,8
JZ Nvr ;wait until Verticle Retrace Ends
ADD word[count],1
RET
;**************************
SECTION .data
count dw 0
It use the Verticle Retrace for timer.
Dex4u
Re:Problem with printing
Posted: Thu Feb 10, 2005 4:31 am
by srg_13
How can you time a delay in C
Thanks,
Stephen
Re:Problem with printing
Posted: Thu Feb 10, 2005 4:37 am
by Pype.Clicker
Stephen wrote:
How can you time a delay in C
By calling a function
Nah, seriously, doing *anything* in C means calling a function. Once you have "inb/outb" in your C runtime, you can use the same trick as dex4u showed in asm:
Code: Select all
/* wait for the screen to retrace. That occurs every 1/70th of seconds on a 70Hz screen, every 1/100th of second on a 100Hz screen, etc.
*/
while (! (inb(0x3da)&8));
// the screen is now retracing
while (inb(0x3da)&8);
If you need *precise* timing, you should consider polling a PIT counter or set up an handler for IRQ0.
Re:Problem with printing
Posted: Thu Feb 10, 2005 4:46 am
by srg_13
Thanks for that.
If you need *precise* timing, you should consider polling a PIT counter or set up an handler for IRQ0.
Well, its only for a splash screen, so i don't really need it to be all that precise.
Re:Problem with printing
Posted: Thu Feb 10, 2005 7:23 am
by B.E
You could you the CPU timer to print a dot every say 1 second.
That way all you have to do is set it up and then let the CPU worry about the rest. but rember to "turn it off" once you have finish.