map073.c
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/*
** Nofrendo (c) 1998-2000 Matthew Conte (matt@conte.com)
**
**
** This program is free software; you can redistribute it and/or
** modify it under the terms of version 2 of the GNU Library General
** Public License as published by the Free Software Foundation.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
** Library General Public License for more details. To obtain a
** copy of the GNU Library General Public License, write to the Free
** Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
**
** Any permitted reproduction of these routines, in whole or in part,
** must bear this legend.
**
**
** map073.c
**
** Mapper #73 (Konami VRC3)
** Implementation by Firebug
** $Id: map073.c,v 1.2 2001/04/27 14:37:11 neil Exp $
**
*/
#include <noftypes.h>
#include <nes_mmc.h>
#include <nes.h>
#include <libsnss.h>
#include <log.h>
static struct
{
bool enabled;
uint32 counter;
} irq;
/**************************/
/* Mapper #73: Salamander */
/**************************/
static void map73_init (void)
{
/* Turn off IRQs */
irq.enabled = false;
irq.counter = 0x0000;
/* Done */
return;
}
/****************************************/
/* Mapper #73 callback for IRQ handling */
/****************************************/
static void map73_hblank (int vblank)
{
/* Counter is M2 based so it doesn't matter whether */
/* the PPU is in its VBlank period or not */
UNUSED (vblank);
/* Increment the counter if it is enabled and check for strike */
if (irq.enabled)
{
/* Is there a constant for cycles per scanline? */
/* If so, someone ought to substitute it here */
irq.counter = irq.counter + 114;
/* Counter triggered on overflow into Q16 */
if (irq.counter & 0x10000)
{
/* Clip to sixteen-bit word */
irq.counter &= 0xFFFF;
/* Trigger the IRQ */
nes_irq ();
/* Shut off IRQ counter */
irq.enabled = false;
}
}
}
/******************************************/
/* Mapper #73 write handler ($8000-$FFFF) */
/******************************************/
static void map73_write (uint32 address, uint8 value)
{
switch (address & 0xF000)
{
case 0x8000: irq.counter &= 0xFFF0;
irq.counter |= (uint32) (value);
break;
case 0x9000: irq.counter &= 0xFF0F;
irq.counter |= (uint32) (value << 4);
break;
case 0xA000: irq.counter &= 0xF0FF;
irq.counter |= (uint32) (value << 8);
break;
case 0xB000: irq.counter &= 0x0FFF;
irq.counter |= (uint32) (value << 12);
break;
case 0xC000: if (value & 0x02) irq.enabled = true;
else irq.enabled = false;
break;
case 0xF000: mmc_bankrom (16, 0x8000, value);
default: break;
}
/* Done */
return;
}
/****************************************************/
/* Shove extra mapper information into a SNSS block */
/****************************************************/
static void map73_setstate (SnssMapperBlock *state)
{
/* TODO: Store SNSS information */
UNUSED (state);
/* Done */
return;
}
/*****************************************************/
/* Pull extra mapper information out of a SNSS block */
/*****************************************************/
static void map73_getstate (SnssMapperBlock *state)
{
/* TODO: Retrieve SNSS information */
UNUSED (state);
/* Done */
return;
}
static map_memwrite map73_memwrite [] =
{
{ 0x8000, 0xFFFF, map73_write },
{ -1, -1, NULL }
};
mapintf_t map73_intf =
{
73, /* Mapper number */
"Konami VRC3", /* Mapper name */
map73_init, /* Initialization routine */
NULL, /* VBlank callback */
map73_hblank, /* HBlank callback */
map73_getstate, /* Get state (SNSS) */
map73_setstate, /* Set state (SNSS) */
NULL, /* Memory read structure */
map73_memwrite, /* Memory write structure */
NULL /* External sound device */
};
/*
** $Log: map073.c,v $
** Revision 1.2 2001/04/27 14:37:11 neil
** wheeee
**
** Revision 1.1 2001/04/27 12:54:40 neil
** blah
**
** Revision 1.1 2001/04/27 10:57:41 neil
** wheee
**
** Revision 1.1 2000/12/30 06:35:05 firebug
** Initial revision
**
**
*/