src/mmc/mmc3.asm

   1 ;
   2 ;    Copyright (C) 2004, 2005 Kent Hansen.
   3 ;
   4 ;    This file is part of Neotoxin.
   5 ;
   6 ;    Neotoxin is free software; you can redistribute it and/or modify
   7 ;    it under the terms of the GNU General Public License as published by
   8 ;    the Free Software Foundation; either version 2 of the License, or
   9 ;    (at your option) any later version.
  10 ;
  11 ;    Neotoxin is distributed in the hope that it will be useful,
  12 ;    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 ;    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 ;    GNU General Public License for more details.
  15 ;
  16 ;    You should have received a copy of the GNU General Public License
  17 ;    along with this program; if not, write to the Free Software
  18 ;    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19 ;
  20
  21 ; Description:
  22 ; MMC3-specific data and code.
  23
  24 .include "mmc3.h"
  25
  26 .dataseg
  27
  28 .public irq_count   .byte
  29
  30 ; The CHR bank indices that are set in NMI.
  31 .public chr_banks   .byte[6]
  32
  33 .public chr_addr_toggle .byte
  34
  35 current_bank    .byte
  36
  37 .codeseg
  38
  39 .public reset_bank
  40 .public set_bank
  41 .public swap_bank
  42
  43 ; Load the 16K bank in current_bank
  44     reset_bank:
  45     lda current_bank
  46 ; Set and load 16K bank in A
  47     set_bank:
  48     sta current_bank
  49 ; Load 16K bank in A, but keep old current_bank value
  50     swap_bank:
  51     asl
  52     ldy #$06    ; command = swap 1st 8K bank
  53     sty MMC3_CTRL_REG
  54     sta MMC3_PAGE_REG
  55     iny         ; command = swap 2nd 8K bank
  56     ora #1
  57     sty MMC3_CTRL_REG
  58     sta MMC3_PAGE_REG
  59     rts
  60
  61 .end