From cee93625989b651cfe91387eabd0abd3f64a00df Mon Sep 17 00:00:00 2001 From: Miquel Sabaté Solà Date: Mon, 27 Nov 2023 10:31:03 +0100 Subject: scroll: Start with the scrolling examples MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This is still work in progress but at least there's some basic structure to it. Signed-off-by: Miquel Sabaté Solà --- scroll/include/ppu.s | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) create mode 100644 scroll/include/ppu.s (limited to 'scroll/include/ppu.s') diff --git a/scroll/include/ppu.s b/scroll/include/ppu.s new file mode 100644 index 0000000..23fd978 --- /dev/null +++ b/scroll/include/ppu.s @@ -0,0 +1,27 @@ +.segment "CODE" + +.scope PPU + CONTROL = $2000 + MASK = $2001 + STATUS = $2002 + SCROLL = $2005 + ADDRESS = $2006 + DATA = $2007 +.endscope + +.macro PPU_ADDR address + lda #.HIBYTE(address) + sta PPU::ADDRESS + lda #.LOBYTE(address) + sta PPU::ADDRESS +.endmacro + +;; WRITE_PPU_DATA is a macro that will write into PPU::ADDRESS the given address +;; and into PPU::DATA the given byte value. +.macro WRITE_PPU_DATA address, value + bit PPU::STATUS + + PPU_ADDR address + lda #value + sta PPU::DATA +.endmacro -- cgit v1.2.3