Reformat main file.
Mostly moved stuff around so that it's in a more sensible order.
This commit is contained in:
Colin McMillen
parent
1319e4f52d
commit
7b6cd3f583
191
pewpew.asm
191
pewpew.asm
@ -30,7 +30,7 @@
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; 0000-000F: scratch space for functions.
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; 0010-0011: controller state of joypad #1.
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; 0012-0013: controller state of joypad #2.
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; 0014-0017: 32-bit counter of vblanks.
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; 0014-0016: 24-bit counter of vblanks.
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; 0018-0019: 16-bit pointer to next random byte.
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; 0020-0021: (x, y) coordinates of player.
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; 0022-0024: RGB color values to use for background color, from [0-31].
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@ -45,8 +45,15 @@
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Start:
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InitializeSNES
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; Store zeroes to the controller status registers.
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; TODO(mcmillen): is this needed? I think the system will overwrite these
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; automatically.
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stz JOY1H
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stz JOY1L
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jsr LoadPaletteAndTileData
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jsr InitializeSpriteTables
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jsr InitializeWorld
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; Set screen mode: 16x16 tiles for backgrounds, mode 1.
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lda #%11000001
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@ -72,29 +79,6 @@ Start:
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lda #%10000001
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sta NMITIMEN
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; Store zeroes to the controller status registers.
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; TODO(mcmillen): is this needed? I think the system will overwrite these
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; automatically.
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stz JOY1H
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stz JOY1L
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; Start the background color as a dark blue.
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lda #4
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sta $24
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; Player's initial starting location.
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lda #(256 / 4)
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sta $20
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lda #((224 - 32) / 2)
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sta $21
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MainLoop:
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wai ; Wait for interrupt.
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jsr JoypadHandler
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jsr SetBackgroundColor
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jsr UpdateGraphics
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jmp MainLoop
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@ -277,35 +261,45 @@ InitializeSpriteTables:
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VBlankHandler:
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jsr VBlankCounter
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jsr DMASpriteTables
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rti
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InitializeWorld:
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; Start the background color as a dark blue.
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lda #4
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sta $24
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; Player's initial starting location.
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lda #(256 / 4)
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sta $20
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lda #((224 - 32) / 2)
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sta $21
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rts
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VBlankCounter:
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; Increment a counter of how many VBlanks we've done.
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inc $14
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lda $14
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cmp #$00
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bne VBlankCounterDone
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inc $15
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lda $15
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cmp #$00
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bne VBlankCounterDone
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inc $16
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lda $16
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cmp #$00
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bne VBlankCounterDone
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inc $17
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VBlankCounterDone:
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MainLoop:
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wai ; Wait for interrupt.
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jsr JoypadDebug
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jsr JoypadHandler
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jsr UpdateWorld
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jsr SetBackgroundColor
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jmp MainLoop
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JoypadDebug:
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; Load joypad registers into RAM for easier inspection.
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lda JOY1L
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sta $10
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lda JOY1H
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sta $11
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lda JOY2L
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sta $12
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lda JOY2H
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sta $13
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rts
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JoypadHandler:
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jsr JoypadDebug ; DEBUG
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JoypadUp:
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lda JOY1H
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@ -413,7 +407,7 @@ JoypadR:
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JoypadB:
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lda JOY1H
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and #$80 ; Start.
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and #$80 ; B
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cmp #$80
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bne JoypadDone
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jsr MaybeShoot
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@ -423,20 +417,6 @@ JoypadDone:
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JoypadDebug:
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; Load joypad registers into RAM for easier inspection.
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lda JOY1L
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sta $10
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lda JOY1H
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sta $11
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lda JOY2L
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sta $12
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lda JOY2H
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sta $13
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rts
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MaybeShoot:
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; If the cooldown timer is non-zero, don't shoot.
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lda $25
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@ -457,39 +437,7 @@ MaybeShoot:
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SetBackgroundColor:
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; $22 $23 $24 are (R, G, B), each ranging from [0-31].
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; The palette color format is 15-bit: [0bbbbbgg][gggrrrrr]
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; Set the background color.
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; Entry 0 corresponds to the SNES background color.
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stz CGADDR
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; Compute and the low-order byte and store it in CGDATA.
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lda $23 ; Green.
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.rept 5
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asl
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.endr
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ora $22 ; Red.
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sta CGDATA
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; Compute the high-order byte and store it in CGDATA.
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lda $24 ; Blue.
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.rept 2
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asl
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.endr
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sta $00
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lda $23 ; Green.
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.rept 3
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lsr
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.endr
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ora $00
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sta CGDATA
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rts
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UpdateGraphics:
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UpdateWorld:
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; Update shot cooldown.
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lda $0025
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cmp #0
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@ -576,6 +524,63 @@ ShotDone:
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SetBackgroundColor:
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; $22 $23 $24 are (R, G, B), each ranging from [0-31].
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; The palette color format is 15-bit: [0bbbbbgg][gggrrrrr]
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; Set the background color.
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; Entry 0 corresponds to the SNES background color.
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stz CGADDR
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; Compute and the low-order byte and store it in CGDATA.
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lda $23 ; Green.
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.rept 5
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asl
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.endr
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ora $22 ; Red.
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sta CGDATA
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; Compute the high-order byte and store it in CGDATA.
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lda $24 ; Blue.
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.rept 2
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asl
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.endr
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sta $00
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lda $23 ; Green.
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.rept 3
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lsr
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.endr
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ora $00
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sta CGDATA
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rts
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VBlankHandler:
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jsr VBlankCounter
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jsr DMASpriteTables
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rti
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VBlankCounter:
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; Increment a counter of how many VBlanks we've done.
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; This is a 24-bit counter. At 60 vblanks/second, this will take over
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; 77 hours to wrap around; that's good enough for me :)
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inc $14
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lda $14
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cmp #$00
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bne VBlankCounterDone
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inc $15
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lda $15
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cmp #$00
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bne VBlankCounterDone
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inc $16
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VBlankCounterDone:
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rts
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DMASpriteTables:
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rep #%00010000 ; 16-bit X/Y.
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sep #%00100000 ; 8-bit A.
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