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.org $1FFF
JMP program
font:
.include "font.bin"
program:
MOV 0, V0 ; Load character #12
MOV 0, V1 ; X position
MOV 0, V2 ; Y position
MOV 1, V3 ; Color (1 = white)
CALL write_char ; Call function to write character
SUS
write_char:
; V0: Character to write
; V1: X position
; V2: Y position
; V3: Color
; Write a character to the screen at (V1, V2) with color V3
MUL V0, 64 ; V0 = Character * 64 (character size)
MOV AX, V0 ; Store result back into character
MUL V2, 64
ADD AX, V1
MOV AX, V4 ; V4 = X position + Y position * 64 (screen index)
MOV V4, [$EFFF] ; Debug
MOV [V0 + $2003], V5 ; Read character (1FFF + 4 since jump address is 1FFF)
MOV V5, [$EFFF] ; Debug
AND V5, $01 ; Mask to get first bit (color)
MOV DX, V5
MOV V5, [$EFFF] ; Debug
MUL V5, V3 ; V5 = Character * Color (color index)
MOV AX, V5 ; Store result into V5
MOV V5, [$EFFF] ; Debug
MOVB V5, [V4 + $402F] ; Write character to screen memory
RET
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