diff options
Diffstat (limited to 'include/reset.s')
| -rw-r--r-- | include/reset.s | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/include/reset.s b/include/reset.s new file mode 100644 index 0000000..e68d3db --- /dev/null +++ b/include/reset.s @@ -0,0 +1,63 @@ +;; Common `reset` procedure for NROM "games". Check `basics/sprite.s` on +;; @mssola/NES for a proper explanation on the code (will be open soon, +;; promise!). +reset: + sei + cld + + ldx #$40 + stx $4017 + + ldx #$ff + txs + + inx + stx $2000 + stx $2001 + stx $4010 + +@vblankwait1: + bit $2002 + 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 $2003 + lda #$02 + sta $4014 + +@vblankwait2: + bit $2002 + bpl @vblankwait2 + + lda #$3F + sta $2006 + lda #$00 + sta $2006 + + lda #$0F + ldx #$20 +@palettes_reset_loop: + sta $2007 + dex + bne @palettes_reset_loop + + jmp main |