First day of advent of code

Signed-off-by: Miquel Sabaté Solà <msabate@suse.com>

5 files changed, 148 insertions, 0 deletions

diff --git a/include/apu.s b/include/apu.s
new file mode 100644
index 0000000..32ccff2
--- /dev/null
+++ b/include/apu.s
@@ -0,0 +1,6 @@
+.segment "CODE"
+
+.scope APU
+    DMC           = $4010
+    FRAME_COUNTER = $4017
+.endscope
diff --git a/include/globals.s b/include/globals.s
new file mode 100644
index 0000000..41d3e6c
--- /dev/null
+++ b/include/globals.s
@@ -0,0 +1,39 @@
+.scope Globals
+    ;;;
+    ;; Temporary values.
+
+    m_tmp_1  = $00
+    m_tmp_2  = $01
+    m_tmp_3  = $02
+    m_tmp_4  = $03
+    m_tmp_5  = $04
+
+    ;; Bit map to be used as flags during execution.
+    m_flags = $20
+
+    ;; Initialize global variables.
+    .proc init
+        lda #0
+        sta m_tmp_1
+        sta m_tmp_2
+        sta m_tmp_3
+        sta m_tmp_4
+        sta m_tmp_5
+        sta m_flags
+        rts
+    .endproc
+.endscope
+
+;; SET_RENDER_FLAG sets the render bit on Globals::m_flags to 1.
+.macro SET_RENDER_FLAG
+  lda #%10000000
+  ora Globals::m_flags
+  sta Globals::m_flags
+.endmacro
+
+;; UNSET_RENDER_FLAG sets the render bit on Globals::m_flags to 0.
+.macro UNSET_RENDER_FLAG
+  lda #%01111111
+  and Globals::m_flags
+  sta Globals::m_flags
+.endmacro
diff --git a/include/oam.s b/include/oam.s
new file mode 100644
index 0000000..ecd1b7d
--- /dev/null
+++ b/include/oam.s
@@ -0,0 +1,13 @@
+.segment "CODE"
+
+.scope OAM
+    ADDR = $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..23fd978
--- /dev/null
+++ b/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
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