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| author | Miquel Sabaté Solà <msabate@suse.com> | 2023-11-12 09:39:05 +0100 |
|---|---|---|
| committer | Miquel Sabaté Solà <mikisabate@gmail.com> | 2025-02-04 21:02:11 +0100 |
| commit | db9cb2118e7b2575ed3b0f535e50dd85c24df25a (patch) | |
| tree | 8bfe1a7e48bd85e2e9ab0c650c248a7bed1955b7 /space/src/vectors/nmi.s | |
| parent | cb854722b9890c171f7d0600812a7e9a3a2a25c9 (diff) | |
| download | code.nes-db9cb2118e7b2575ed3b0f535e50dd85c24df25a.tar.gz code.nes-db9cb2118e7b2575ed3b0f535e50dd85c24df25a.zip | |
space: Simplify the code and its goals
Originally this was supposed to be a sort of mini game, but that would
have probably made it too complex for newcomers. Thus, let's just keep
it to subpixel movement and shooting bullets, which is already a big
step from the `basics/sprite.s` example.
Signed-off-by: Miquel Sabaté Solà <msabate@suse.com>
Diffstat (limited to 'space/src/vectors/nmi.s')
| -rw-r--r-- | space/src/vectors/nmi.s | 24 |
1 files changed, 21 insertions, 3 deletions
diff --git a/space/src/vectors/nmi.s b/space/src/vectors/nmi.s index 4bc3dde..e049239 100644 --- a/space/src/vectors/nmi.s +++ b/space/src/vectors/nmi.s @@ -1,14 +1,32 @@ -;; Non-Maskable Interrupts handler. +;; See `basics/sprite.s` for more info. I'm not doing anything fancier here. nmi: - ;; As mentioned on the `main` subroutine, rendering will be skipped until - ;; the proper flag is set. bit $20 bpl @next + ;; Save registers. + pha + txa + pha + tya + pha + ;; We can start rendering stuff. OAM_WRITE_SPRITES + ;; Reset scroll. + bit $2002 ; PPUSTATUS + lda #$00 + sta $2005 ; PPUSCROLL + sta $2005 ; PPUSCROLL + ;; And unset the render flag so the `main` code is unblocked. UNSET_RENDER_FLAG + + ;; Restore registers. + pla + tay + pla + tax + pla @next: rti |