display default palette

[bootboot] / bb.asm

diff --git a/bb.asm b/bb.asm
index fee43e4..397bb30 100644 (file)
--- a/bb.asm
+++ b/bb.asm
@@ -96,7 +96,7 @@ clearscreen:
        ret
 
 saved_drive_num:
-       db 0 ; declare byte 0
+       db 0 ; define byte 0
 
 ; assembler trick: write as many 0 needed to fill 510 bytes
 ; $ <- means here
@@ -104,7 +104,29 @@ saved_drive_num:
        dw 0aa55h
 
 sector_2:
-       mov ax, 5
-       call clearscreen
+; disp palette
+       mov ax, 0a000h  ; video segment points to video memory
+       mov ds, ax
+       mov bx, 0               ; video offset
+       mov cx, 0               ; y
+.y_loop:
+       mov dx, 0               ; x
+.x_loop:
+       mov ax, dx
+       test ax, 0ff00h ; lower 8 bits 0, highest 1, Z flag is set while < 256, test = and but doesnt change ax 
+       jz      .skip_clear_ax
+       mov al, 0
+.skip_clear_ax:
+       mov [bx], al    ; pixel written on screen
+       inc bx                  ; increment
+       inc dx
+       cmp dx, 320
+       jnz .x_loop
+       inc cx
+       cmp cx, 200
+       jnz .y_loop
+
+; fix palette (256 colors)
+       
 .inf_loop:
        jmp .inf_loop