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SixtyPical/eg/atari2600/smiley.60p
2018-03-29 14:45:28 +01:00

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