Commit: 044465644cfc3227b596dfc177607bad7523d0a9
Author: Vi Grey
Date: 2020-08-22 20:16 UTC
Summary: Initial commit

 hello-world-nes.asm | 163 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 hello-world-nes.nes | Bin 0 -> 24592 bytes
 tileset.chr         | Bin 0 -> 8192 bytes
 3 files changed, 163 insertions(+)


diff --git a/hello-world-nes.asm b/hello-world-nes.asm
new file mode 100644
index 0000000..dd57df5
--- /dev/null
+++ b/hello-world-nes.asm
@@ -0,0 +1,163 @@
+; Copyright (C) 2020, Vi Grey
+; All rights reserved.
+;
+; Redistribution and use in source and binary forms, with or without
+; modification, are permitted provided that the following conditions
+; are met:
+;
+; 1. Redistributions of source code must retain the above copyright
+;    notice, this list of conditions and the following disclaimer.
+; 2. Redistributions in binary form must reproduce the above copyright
+;    notice, this list of conditions and the following disclaimer in the
+;    documentation and/or other materials provided with the distribution.
+;
+; THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+; ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+; IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+; ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
+; FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+; DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+; OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+; HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+; LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+; OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+; SUCH DAMAGE.
+
+; Constants
+PPU_CTRL            = $2000
+PPU_MASK            = $2001
+PPU_STATUS          = $2002
+PPU_OAM_ADDR        = $2003
+PPU_OAM_DATA        = $2004
+PPU_SCROLL          = $2005
+PPU_ADDR            = $2006
+PPU_DATA            = $2007
+APU_DMC             = $4010
+OAM_DMA             = $4014
+APU_FRAME_COUNTER   = $4017
+CALLBACK            = $BFFA
+
+; Variables
+.enum $0000
+  addr  dsb 2
+.ende
+
+; iNES header
+  .db "NES", $1A
+  .db $01 ; 16KB PRG
+  .db $01 ; 8KB CHR
+  .db $00 ; Horizontal Mirroring
+  .db $00
+  .db 0, 0, 0, 0, 0, 0, 0, 0
+
+; Set PRG start to 0xC000
+.base $8000
+
+RESET:
+  sei ; Disable Interrupts
+  cld ; Set Decimal Mode to 0
+  lda #%01000000
+  sta APU_FRAME_COUNTER ; Inhibit IRQ
+  ldx #$FF
+  txs ; Set stack register to 0xFF
+  inx ; Increment X from 0xFF to 0x00
+  stx PPU_MASK ; No sprites or background tiles on leftmost 8 pixels
+  stx PPU_CTRL
+  stx APU_DMC ; Disable APU DMC
+
+InitialVWait:
+  lda PPU_STATUS
+  bpl InitialVWait ; Wait for vblank to continue
+InitialVWait2:
+  lda PPU_STATUS
+  bpl InitialVWait2 ; Wait for vblank to continue
+; PPU is now ready
+
+InitializePPUNametableRAM:
+  lda PPU_STATUS
+  lda #$20
+  sta PPU_ADDR
+  lda #$00
+  sta PPU_ADDR
+  ldy #$08
+InitializePPUNametableRAMLoop:
+  sta PPU_DATA
+  inx
+  bne InitializePPUNametableRAMLoop
+    dey
+    bne InitializePPUNametableRAMLoop
+
+SetPalette:
+  lda PPU_STATUS
+  lda #$3F
+  sta PPU_ADDR
+  ldx #$00
+  stx PPU_ADDR
+  lda #$0F
+  sta PPU_DATA
+  sta PPU_DATA
+  sta PPU_DATA
+  lda #$20
+  sta PPU_DATA
+
+DrawHelloWorld:
+  ldy PPU_STATUS
+  sta PPU_ADDR
+  lda #$42
+  sta PPU_ADDR
+DrawHELLoop:
+  inx ; H E L
+  stx PPU_DATA
+  cpx #$03
+  bcc DrawHELLoop
+DrawLOCommaLoop:
+  stx PPU_DATA
+  inx ; O L , W
+  cpx #$06
+  bcc DrawLOCommaLoop
+DrawHelloWorldContinue:
+  lda #$00 ; Blank Space
+  sta PPU_DATA
+  stx PPU_DATA
+  ldy #$04 ; O
+  sty PPU_DATA
+  inx ; R
+  stx PPU_DATA
+  dey ; L
+  sty PPU_DATA
+  inx ; D
+  stx PPU_DATA
+  inx ; !
+  stx PPU_DATA
+
+  lda #%10000000
+  sta PPU_CTRL
+
+; Infinite Loop
+Forever:
+  jmp Forever
+
+NMI:
+  ldx #$00
+  stx PPU_OAM_ADDR
+  lda PPU_STATUS
+Draw:
+  lda #%00011110
+  sta PPU_MASK
+ResetScroll:
+  stx PPU_SCROLL
+  stx PPU_SCROLL
+EnableNMI:
+  lda #%10000000
+  sta PPU_CTRL
+  rti
+
+  ; Pad everything up to FFFA with 0x00 bytes
+  .pad CALLBACK, #$00
+
+  .dw  NMI    ; NMI Address
+  .dw  RESET  ; Reset Address
+  .dw  0      ; IRQ Address
+
+.base $0000
+  .incbin "tileset.chr"
diff --git a/hello-world-nes.nes b/hello-world-nes.nes
new file mode 100644
index 0000000..4b66d02
Binary files /dev/null and b/hello-world-nes.nes differ
diff --git a/tileset.chr b/tileset.chr
new file mode 100644
index 0000000..2630f75
Binary files /dev/null and b/tileset.chr differ