diff options
| -rw-r--r-- | src/jetpac.s | 10 | ||||
| -rw-r--r-- | src/vectors.s | 38 |
2 files changed, 23 insertions, 25 deletions
diff --git a/src/jetpac.s b/src/jetpac.s index 65b5d11..10f6df3 100644 --- a/src/jetpac.s +++ b/src/jetpac.s @@ -45,9 +45,17 @@ .include "vectors.s" .proc main - ;; Disable the PPU. + ;; Disable the PPU and zero out variables which shadow PPU registers. lda #0 sta PPU::MASK + sta PPU::zp_mask + sta PPU::zp_control + + ;; Initialize other global variables which the rest of the game assume to + ;; have zero as their initial values. + sta Globals::zp_flags + sta Joypad::zp_buttons1 + sta Joypad::zp_buttons2 ;; Initialize the assets for the game. jsr Assets::init diff --git a/src/vectors.s b/src/vectors.s index 559a59d..8928aaf 100644 --- a/src/vectors.s +++ b/src/vectors.s @@ -5,64 +5,54 @@ ;; Pretty standard reset function, nothing crazy. .proc reset + ;; Disable interrupts and decimal mode. sei cld + ;; Disable APU frame counter. ldx #$40 stx APU::FRAME_COUNTER + ;; Setup the stack. ldx #$FF txs + ;; Disable NMIs and the APU's DMC. inx stx PPU::CONTROL stx PPU::MASK stx APU::DMC + ;; First PPU wait. bit PPU::STATUS @vblankwait1: bit PPU::STATUS bpl @vblankwait1 - ldx #0 - lda #0 -@ram_reset_loop: - sta $000, x - sta $100, x - sta $300, x - sta $400, x - sta $500, x - sta $600, x - sta $700, x - inx - bne @ram_reset_loop - + ;; Reset all sprites by simply moving the Y coordinate out of screen. lda #$EF + ldx #0 @sprite_reset_loop: sta $200, x inx + inx + inx + inx bne @sprite_reset_loop + ;; DMA setup for sprite reset. lda #$00 sta OAM::ADDRESS lda #$02 sta OAM::DMA + ;; Second PPU wait. After that the PPU is stable. @vblankwait2: bit PPU::STATUS bpl @vblankwait2 - lda #$3F - sta PPU::ADDRESS - lda #$00 - sta PPU::ADDRESS - - lda #$0F - ldx #$20 -@palettes_reset_loop: - sta PPU::DATA - dex - bne @palettes_reset_loop + ;; NOTE: palettes are not initialized here as it's going to be one of the + ;; first things done on `main` code. jmp main .endproc |