239 lines
5.1 KiB
NASM
239 lines
5.1 KiB
NASM
; .setcpu "65C02"
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.include "./macro.inc"
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.org $8000
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n = $01 ; temporary storage for data stack operations
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temp = $20 ; scratchpad page
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cursor = $300
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cursor_x = cursor
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cursor_y = cursor + 1
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rand_index = $200
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reset:
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sei
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ldx #0; initialize data stack pointer
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init:
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cli
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main:
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jsr print
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jsr rand_draw
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jmp main
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newline: ; sets cursor to start of next line
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stz cursor_x
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lda cursor_y
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cmp #28
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bne .end
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stz cursor_y
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rts
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.end:
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inc cursor_y
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rts
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text:
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.byte 1,2,3,2,4
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.asciiz "- george loves u <3"
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random_y:
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.byte 25,12,0,20,4,25,5,13
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.byte 20, 1, 1, 22, 12, 19, 19, 19
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.byte 9, 0, 4, 18, 13, 14, 4, 16
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.byte 8, 17, 21, 14, 23, 21, 9, 0
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.byte 14, 10, 14, 2, 26, 18, 15, 23
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.byte 12, 2, 5, 4, 25, 20, 27, 4
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.byte 28, 21, 3, 22, 11, 25, 2, 25
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.byte 13, 17, 17, 24, 8, 8, 20, 21
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.byte 11, 24, 27, 25, 8, 12, 7, 0
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.byte 27, 12, 19, 27, 10, 3, 19, 2
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.byte 2, 23, 22, 5, 26, 28, 4, 16
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.byte 18, 7, 10, 9, 6, 19, 9, 2
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.byte 14, 8, 14, 18, 18, 2, 13, 0
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.byte 15, 26, 3, 23, 17, 12, 18, 11
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.byte 4, 16, 17, 22, 9, 25, 3, 15
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.byte 28, 3, 6, 14, 25, 5, 21, 8
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.byte 15, 18, 15, 5, 28, 6, 15, 4
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.byte 10, 1, 16, 24, 6, 9, 22, 3
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.byte 17, 18, 10, 19, 27, 11, 22, 16
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.byte 22, 17, 15, 6, 23, 11, 11, 11
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.byte 4, 15, 5, 25, 19, 1, 8, 26
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.byte 21, 20, 17, 27, 11, 3, 11, 20
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.byte 15, 28, 0, 6, 14, 23, 20, 21
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.byte 17, 20, 16, 15, 19, 6, 21, 19
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.byte 15, 27, 1, 22, 7, 0, 5, 2
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.byte 14, 24, 15, 4, 20, 16, 1, 14
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.byte 4, 16, 4, 8, 13, 26, 3, 9
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.byte 12, 25, 5, 0, 7, 17, 14, 20
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.byte 2, 26, 2, 27, 18, 23, 5, 8
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.byte 4, 21, 10, 11, 28, 22, 6, 6
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.byte 10, 13, 23, 12, 20, 28, 20, 1
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.byte 27, 19, 25, 6, 1, 10, 1
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random_x:
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.byte 42, 59, 11, 5, 18, 0, 26, 1
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.byte 61, 16, 1, 51, 36, 47, 23, 1
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.byte 16, 50, 46, 4, 55, 31, 15, 2
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.byte 45, 21, 59, 53, 15, 43, 0, 2
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.byte 64, 31, 38, 41, 25, 12, 12, 3
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.byte 30, 13, 64, 44, 21, 8, 48, 3
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.byte 46, 1, 2, 33, 4, 32, 59, 28
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.byte 4, 24, 58, 53, 21, 41, 30, 2
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.byte 56, 53, 31, 10, 42, 12, 9, 54
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.byte 14, 14, 24, 29, 43, 60, 54, 26
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.byte 5, 53, 17, 55, 27, 46, 31, 3
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.byte 26, 44, 63, 30, 10, 34, 62, 48
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.byte 42, 47, 51, 7, 55, 32, 14, 21
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.byte 15, 26, 52, 37, 48, 0, 13, 2
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.byte 50, 20, 35, 32, 8, 41, 2, 24
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.byte 18, 9, 52, 22, 52, 12, 19, 32
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.byte 29, 46, 34, 58, 54, 51, 43, 57
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.byte 62, 10, 12, 57, 36, 39, 4, 30
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.byte 38, 9, 30, 32, 33, 57, 3, 25
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.byte 21, 36, 59, 30, 19, 39, 9, 60
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.byte 34, 50, 52, 37, 34, 42, 3, 33
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.byte 40, 19, 2, 26, 10, 38, 46, 30
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.byte 3, 1, 19, 16, 26, 58, 42, 49
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.byte 63, 1, 63, 41, 0, 21, 41, 19
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.byte 21, 45, 44, 52, 20, 5, 11, 64
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.byte 1, 62, 16, 5, 5, 8, 58, 56
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.byte 16, 26, 6, 37, 19, 16, 25, 29
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.byte 64, 59, 16, 6, 41, 28, 8, 51
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.byte 54, 5, 19, 28, 13, 38, 52, 35
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.byte 42, 13, 34, 33, 61, 61, 7, 27
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.byte 38, 33, 9, 57, 10, 30, 8, 4
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.byte 46, 3, 39, 46, 62, 20, 48, 7
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; increments the cursor line by line, looping to (0, 0) after (63, 28)
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inc_cursor:
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lda cursor_x
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cmp #63
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beq .newline
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inc cursor_x
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rts
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.newline:
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lda cursor_y
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cmp #28
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beq .newscreen
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stz cursor_x
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inc cursor_y
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rts
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.newscreen:
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stz cursor_y
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stz cursor_x
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rts
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; zeroes out the display, resets cursor to 0,0
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clear:
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lda #0
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ldy #0
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.loop:
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sta $6000,y
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sta $6100,y
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sta $6200,y
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sta $6300,y
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sta $6400,y
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sta $6500,y
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sta $6600,y
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sta $6700,y ; this goes slightly over but it's fine
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iny
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bne .loop
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stz cursor
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stz cursor + 1
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rts
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; prints string from cursor position, stopping at end of string or at 256 chars, whichever comes first
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; $6000 + (64*Y) + X
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; THIS WILL WRITE OUT OF BOUNDS IF THE CURSOR IS OUT OF BOUNDS/STRING IS TOO LONG
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; TODO: figure out a simple way of writing arbitrary length strings
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print:
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jsr cursor_addr
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ldy #0
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; y_overflow = temp + 5
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.loop:
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lda text, y
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beq .end
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sta (temp), y
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iny
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bra .loop
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.end:
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rts
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; calculates real vram address from cursor (x, y)
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cursor_addr:
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stz temp
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stz temp + 1
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lda cursor_y
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beq .add_x ; if y's zero just add x
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.y_mult:
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; multiply by 64
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clc
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asl
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rol temp + 1
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asl
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rol temp + 1
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asl
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rol temp + 1
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asl
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rol temp + 1
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asl
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rol temp + 1
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asl
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rol temp + 1
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sta temp
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.add_x:
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clc
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lda cursor_x
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adc temp
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sta temp
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lda #0
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adc temp + 1
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sta temp + 1
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clc
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lda #$60
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adc temp + 1
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sta temp + 1
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rts
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rand_draw:
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ldx rand_index
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lda random_x, x
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sta cursor_x
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lda random_y, x
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sta cursor_y
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jsr cursor_addr
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inc rand_index
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rts
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isr: ; interrupt service routine
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pha
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phx
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phy
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; jsr irq
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ply
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plx
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pla
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rti
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.include "math.inc"
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.org $fffc
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.word reset
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.word isr
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