Initial commit

Add the basic structure and the first example: managing controller
input.

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

1 files changed, 90 insertions, 0 deletions

diff --git a/examples/wrapper.s b/examples/wrapper.s
new file mode 100644
index 0000000..673c697
--- /dev/null
+++ b/examples/wrapper.s
@@ -0,0 +1,90 @@
+;;;
+;; This is an empty wrapper for the NES. It does some basic hardware
+;; initialization and finally calls a `Main` subroutine that is to be provided
+;; by another file. After that, it loops indefinitely.
+;;
+;; There are some variations of this file already, I just took it from
+;; NESHacker: https://github.com/NesHacker (definitely check his Youtube
+;; channel, it's extra-dope!); originally licensed under the MIT License.
+;;;
+
+.import Main
+
+.segment "HEADER"
+  .byte $4E, $45, $53, $1A  ; iNES header identifier
+  .byte 2                   ; 2x 16KB PRG-ROM Banks
+  .byte 1                   ; 1x  8KB CHR-ROM
+  .byte $01, $00            ; mapper 0, vertical mirroring
+
+.segment "VECTORS"
+  .addr nmi
+  .addr reset
+  .addr 0
+
+.segment "STARTUP"
+
+.segment "CHARS"
+
+.segment "CODE"
+
+.proc nmi
+  bit $2002
+  lda #0
+  sta $2006
+  sta $2006
+  rti
+.endproc
+
+.proc ResetPalettes
+  bit $2002
+  lda #$3f
+  sta $2006
+  lda #$00
+  sta $2006
+  lda #$0F
+  ldx #$20
+@paletteLoadLoop:
+  sta $2007
+  dex
+  bne @paletteLoadLoop
+  rts
+.endproc
+
+.proc reset
+  sei
+  cld
+  ldx #%01000000
+  stx $4017
+  ldx #$ff
+  txs
+  ldx #0
+  stx $2000
+  stx $2001
+  stx $4010
+  bit $2002
+@vblankWait1:
+  bit $2002
+  bpl @vblankWait1
+@clearMemory:
+  lda #$00
+  sta $0000, x
+  sta $0100, x
+  sta $0200, x
+  sta $0300, x
+  sta $0400, x
+  sta $0500, x
+  sta $0600, x
+  sta $0700, x
+  inx
+  bne @clearMemory
+@vblankWait2:
+  bit $2002
+  bpl @vblankWait2
+  jsr ResetPalettes
+main:
+  jsr Main
+  lda #%00001000
+  sta $2001
+endlessLoop:
+  jmp endlessLoop
+.endproc