From 2627b459d9a19ce7f1b7f3a359dca3b30b66b34e Mon Sep 17 00:00:00 2001
From: Miquel Sabaté Solà <mikisabate@gmail.com>
Date: Wed, 12 Mar 2025 22:38:12 +0100
Subject: Start with a skeleton for the project
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Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
---
 include/apu.s     |  4 ++++
 include/globals.s | 34 ++++++++++++++++++++++++++++++++++
 include/oam.s     | 11 +++++++++++
 include/ppu.s     |  8 ++++++++
 4 files changed, 57 insertions(+)
 create mode 100644 include/apu.s
 create mode 100644 include/globals.s
 create mode 100644 include/oam.s
 create mode 100644 include/ppu.s

(limited to 'include')

diff --git a/include/apu.s b/include/apu.s
new file mode 100644
index 0000000..65d9876
--- /dev/null
+++ b/include/apu.s
@@ -0,0 +1,4 @@
+.scope APU
+    DMC           = $4010
+    FRAME_COUNTER = $4017
+.endscope
diff --git a/include/globals.s b/include/globals.s
new file mode 100644
index 0000000..d22b217
--- /dev/null
+++ b/include/globals.s
@@ -0,0 +1,34 @@
+;; Global variables used throughout the code base.
+.scope Globals
+    ;;;
+    ;; Argument values as defined in https://github.com/mssola/style.nes. Note
+    ;; that these variables can also be used as temporary variables.
+    zp_arg0 = $00
+    zp_arg1 = $01
+    zp_arg2 = $02
+    zp_arg3 = $03
+    zp_arg4 = $04
+
+    ;;;
+    ;; Random values that can be used inside of functions for temporary values
+    ;; so `zp_argX` variables are not overwritten as often.
+    zp_tmp0 = $05
+    zp_tmp1 = $06
+    zp_tmp2 = $07
+    zp_tmp3 = $08
+
+    ;;;
+    ;; Reserve a byte of memory for preserving indices on memory. This is needed
+    ;; whenever the `x` and `y` registers might not be reliable because of
+    ;; underlying `jsr` calls that might tamper with their values. Sometimes
+    ;; saving the value in memory is enough instead of playing with the stack.
+    zp_idx = $09
+
+    ;; Flags that manage the state of the game.
+    ;;
+    ;; | Bit | Short name | Meaning when set                                            |
+    ;; |-----+------------+-------------------------------------------------------------|
+    ;; |   7 | render     | Game logic is over, block main code until NMI code is over. |
+    ;; | 6-0 | -          | Unused                                                      |
+    zp_flags = $20
+.endscope
diff --git a/include/oam.s b/include/oam.s
new file mode 100644
index 0000000..22935b2
--- /dev/null
+++ b/include/oam.s
@@ -0,0 +1,11 @@
+.scope OAM
+    ADDRESS = $2003
+    DMA     = $4014
+.endscope
+
+.macro OAM_WRITE_SPRITES
+    lda #$00
+    sta OAM::ADDR
+    lda #$02
+    sta OAM::DMA
+.endmacro
diff --git a/include/ppu.s b/include/ppu.s
new file mode 100644
index 0000000..fa0df19
--- /dev/null
+++ b/include/ppu.s
@@ -0,0 +1,8 @@
+.scope PPU
+    CONTROL = $2000
+    MASK    = $2001
+    STATUS  = $2002
+    SCROLL  = $2005
+    ADDRESS = $2006
+    DATA    = $2007
+.endscope
-- 
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