183 lines
2.6 KiB
NASM
183 lines
2.6 KiB
NASM
// vim: filetype=kickass
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//
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// clear_screen
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//
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// Destroys: a, y
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//
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clear_screen:
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ldy #0
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!loop:
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lda #' '
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sta SCREEN_RAM, y
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sta SCREEN_RAM + $0100, y
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sta SCREEN_RAM + $0200, y
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sta SCREEN_RAM + $0300, y
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sta SCREEN_RAM + $03e7, y
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lda #1
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sta COLOR_RAM, y
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sta COLOR_RAM + $0100, y
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sta COLOR_RAM + $0200, y
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sta COLOR_RAM + $0300, y
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sta COLOR_RAM + $03e7, y
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iny
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bne !loop-
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lda #<SCREEN_RAM
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sta cursor_pointer_lo
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lda #>SCREEN_RAM
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sta cursor_pointer_hi
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lda #23
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sta $d018
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rts
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//
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// print_carriage_return
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//
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// Input:
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// - cursor_pointer_{lo,hi} - Cursor pointer.
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//
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// Destroys: a, zp_temp
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//
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print_newline:
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sec
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lda $05
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adc #40
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sta cursor_pointer_lo
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bcc !done+
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inc cursor_pointer_hi
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!done:
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rts
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//
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// print_carriage_return
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//
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// Input:
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// - cursor_pointer_{lo,hi} - Cursor pointer.
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//
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// Destroys: a, zp_temp
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//
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print_carriage_return:
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// Subtract SCREEN_RAM from cursor pointer
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sec
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lda cursor_pointer_hi
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sbc #>SCREEN_RAM
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sta cursor_pointer_hi
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// Divide the cursor position by 40 (one row)
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i16_div8(cursor_pointer_lo, cursor_pointer_hi)
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// At this point, the pointer fits in a 8-bit register
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lda cursor_pointer_lo
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i8_div5_a()
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// Multiply it by 40 again
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i8_mul5_a()
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sta cursor_pointer_lo
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i16_mul8(cursor_pointer_lo, cursor_pointer_hi)
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// Add SCREEN_RAM back
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clc
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lda cursor_pointer_hi
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adc #>SCREEN_RAM
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sta cursor_pointer_hi
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rts
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//
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// write_string
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//
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// Input:
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// - $03-$04 - Pointer to null-terminated string.
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// - $05-$06 - Cursor pointer.
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//
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// Destroys: a, x, y
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//
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write_string:
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ldx #0
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ldy #0
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!loop:
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lda ($03), y
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beq !done+
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cmp #'\r'
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beq !carriage_return+
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cmp #'\n'
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beq !newline+
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sta (cursor_pointer_lo, x)
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i16_inc(cursor_pointer_lo, cursor_pointer_hi)
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iny
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jmp !loop-
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!newline:
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jsr print_newline
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!carriage_return:
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jsr print_carriage_return
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iny
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jmp !loop-
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!done:
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rts
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print_hex_0x:
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sta zp_temp
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ldx #0
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lda #'0'
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sta (cursor_pointer_lo, x)
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i16_inc(cursor_pointer_lo, cursor_pointer_hi)
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lda #'x'
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sta (cursor_pointer_lo, x)
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i16_inc(cursor_pointer_lo, cursor_pointer_hi)
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lda zp_temp
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// fallthrough
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print_hex:
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ldx #0
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sta zp_temp
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lsr
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lsr
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lsr
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lsr
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tay
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lda !hex_chars+, y
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sta (cursor_pointer_lo, x)
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i16_inc(cursor_pointer_lo, cursor_pointer_hi)
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lda zp_temp
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and #$0f
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tay
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lda !hex_chars+, y
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sta (cursor_pointer_lo, x)
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i16_inc(cursor_pointer_lo, cursor_pointer_hi)
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rts
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!hex_chars:
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.text "0123456789ABCDEF"
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