From ba0cf9e5293f258c58ced1fcc47f558e7419dae4 Mon Sep 17 00:00:00 2001 From: Miquel Sabaté Solà Date: Mon, 10 Mar 2025 22:55:41 +0100 Subject: Provide an example on multiscreen scrolling MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Signed-off-by: Miquel Sabaté Solà --- scroll/include/reset.s | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) create mode 100644 scroll/include/reset.s (limited to 'scroll/include/reset.s') diff --git a/scroll/include/reset.s b/scroll/include/reset.s new file mode 100644 index 0000000..2402795 --- /dev/null +++ b/scroll/include/reset.s @@ -0,0 +1,62 @@ +;; Check `basics/sprite.s` for a deeper look on the logic below. +.proc reset + sei + cld + + ldx #$40 + stx APU::FRAME_COUNTER + + ldx #$FF + txs + + inx + stx PPU::CONTROL + stx PPU::MASK + stx APU::DMC + +@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 $700, x + inx + bne @ram_reset_loop + + lda #$EF +@sprite_reset_loop: + sta $200, x + inx + bne @sprite_reset_loop + + lda #$00 + sta OAM::ADDR + lda #$02 + sta OAM::DMA + +@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 + + jmp main +.endproc -- cgit v1.2.3