189 lines
3.6 KiB
Plaintext
189 lines
3.6 KiB
Plaintext
// smiley.60p - SixtyPical translation of smiley.oph (2018),
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// which is itself a stripped-down version of atari-2600-example.oph
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// SPDX-FileCopyrightText: Chris Pressey, the author of this work, has dedicated it to the public domain.
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// For more information, please refer to <https://unlicense.org/>
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// SPDX-License-Identifier: Unlicense
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byte VSYNC @ $00
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byte VBLANK @ $01
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byte WSYNC @ $02
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byte NUSIZ0 @ $04
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byte NUSIZ1 @ $05
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byte COLUPF @ $08
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byte COLUBK @ $09
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byte PF0 @ $0D
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byte PF1 @ $0E
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byte PF2 @ $0F
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byte SWCHA @ $280
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byte INTIM @ $284
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byte TIM64T @ $296
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byte CTRLPF @ $0A
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byte COLUP0 @ $06
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byte COLUP1 @ $07
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byte GP0 @ $1B
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byte GP1 @ $1C
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byte HMOVE @ $2a
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byte RESP0 @ $10
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byte RESP1 @ $11
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byte colour @ $80
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byte luminosity @ $81
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byte joystick_delay @ $82
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byte table[8] image_data : 126, 129, 153, 165, 129, 165, 129, 126
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// %01111110
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// %10000001
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// %10011001
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// %10100101
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// %10000001
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// %10100101
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// %10000001
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// %01111110
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define vertical_blank routine
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outputs VSYNC, WSYNC, TIM64T
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trashes a, x, z, n
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{
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ld x, $00
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ld a, $02
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st a, WSYNC
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st a, WSYNC
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st a, WSYNC
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st a, VSYNC
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st a, WSYNC
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st a, WSYNC
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ld a, $2C
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st a, TIM64T
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ld a, $00
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st a, WSYNC
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st a, VSYNC
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}
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define display_frame routine
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inputs INTIM, image_data
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outputs WSYNC, HMOVE, VBLANK, RESP0, GP0, PF0, PF1, PF2, COLUPF, COLUBK
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trashes a, x, y, z, n
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{
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repeat {
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ld a, INTIM
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} until z
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//; (After that loop finishes, we know the accumulator must contain 0.)
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st a, WSYNC
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st a, HMOVE
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st a, VBLANK
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//;
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//; Wait for $3f (plus one?) scan lines to pass, by waiting for
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//; WSYNC that many times.
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//;
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ld x, $3F
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repeat {
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st a, WSYNC
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dec x
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} until n
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st a, WSYNC
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//;
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//; Delay while the raster scans across the screen. The more
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//; we delay here, the more to the right the player will be when
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//; we draw it.
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//;
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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//;
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//; OK, *now* display the player.
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//;
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st a, RESP0
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//;
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//; Loop over the rows of the sprite data, drawing each to the screen
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//; over four scan lines.
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//;
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//; TODO understand this better and describe it!
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//;
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ld y, $07
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for y down to 0 {
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ld a, image_data + y
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st a, GP0
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st a, WSYNC
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st a, WSYNC
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st a, WSYNC
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st a, WSYNC
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} // FIXME original was "dec y; bpl _image_loop"
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ld a, $00
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st a, GP0
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//;
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//; Turn off screen display and clear display registers.
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//;
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ld a, $02
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st a, WSYNC
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st a, VBLANK
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ld a, $00
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st a, PF0
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st a, PF1
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st a, PF2
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st a, COLUPF
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st a, COLUBK
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}
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define colourize_player routine
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inputs colour, luminosity
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outputs COLUP0
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trashes a, z, c, n
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{
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ld a, colour
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st off, c
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shl a
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shl a
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shl a
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shl a
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or a, luminosity
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st a, COLUP0
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}
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define main routine
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inputs image_data, INTIM
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outputs CTRLPF, colour, luminosity, NUSIZ0, VSYNC, WSYNC, TIM64T, HMOVE, VBLANK, RESP0, GP0, PF0, PF1, PF2, COLUPF, COLUBK, COLUP0
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trashes a, x, y, z, c, n
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{
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ld a, $00
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st a, CTRLPF
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ld a, $0c
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st a, colour
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ld a, $0a
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st a, luminosity
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ld a, $00
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st a, NUSIZ0
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repeat {
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call vertical_blank
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call display_frame
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call colourize_player
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} forever
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}
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