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/*
ezx81 - X11 ZX81 emulator
Copyright (C) 2003 Ian Cowburn (ianc@noddybox.demon.co.uk)
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-------------------------------------------------------------------------
Provides the emulation for the ZX81
*/
static const char ident[]="$Id$";
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "zx81.h"
#include "config.h"
#include "exit.h"
static const char ident_h[]=EZX81ZX81H;
/* ---------------------------------------- STATICS
*/
static const int ROMLEN=0x2000;
static const int ROM_SAVE=0x2fc;
static const int ROM_LOAD=0x347;
/* These assume a 320x200 screen
*/
static const int OFF_X=(320-256)/2;
static const int OFF_Y=(200-192)/2;
static Z80Byte mem[0x10000];
static Z80Word RAMBOT=0;
static Z80Word RAMTOP=0;
static Z80Word RAMLEN=0;
/* ---------------------------------------- PRIVATE FUNCTIONS
*/
void ULA_Video_Shifter(Z80 *z80, Z80Byte val)
{
}
/* ---------------------------------------- EXPORTED INTERFACES
*/
void ZX81Init(void)
{
FILE *fp;
Z80Word f;
if (!(fp=fopen(SConfig(CONF_ROMFILE),"rb")))
Exit("Failed to open ZX81 ROM - %s\n",SConfig(CONF_ROMFILE));
if (fread(mem,1,ROMLEN,fp)!=ROMLEN)
{
fclose(fp);
Exit("ROM file must be %d bytes long\n",ROMLEN);
}
/* Mirror the ROM
*/
memcpy(mem+ROMLEN,mem,ROMLEN);
RAMBOT=0x4000;
/* Memory size (1 or 16K)
*/
if (IConfig(CONF_MEMSIZE)==16)
RAMLEN=0x2000;
else
RAMLEN=0x400;
RAMTOP=RAMBOT+RAMLEN;
for(f=RAMBOT;f<=RAMTOP;f++)
mem[f]=0;
}
Z80Byte ZX81ReadMem(Z80 *z80, Z80Word addr)
{
/* Memory reads above 32K invoke the ULA
*/
if (addr>0x7fff)
{
Z80Byte b;
/* B6 of R is tied to the IRQ line (only when HSYNC active?)
if ((HSYNC)&&(!(z80->R&0x40)))
z80->IRQ=TRUE;
*/
b=mem[addr&0x7fff];
/* If bit 6 of the opcode is set the opcode is sent as is to the
Z80. If it's not, the byte is interretted by the ULA.
*/
if (b&0x40)
{
ULA_Video_Shifter(z80,0);
}
else
{
ULA_Video_Shifter(z80,b);
b=0;
}
return b;
}
else
return mem[addr&0x7fff];
}
void ZX81WriteMem(Z80 *z80, Z80Word addr, Z80Byte val)
{
if (addr>=RAMBOT && addr<=RAMTOP)
mem[addr&0x7fff]=val;
}
Z80Byte ZX81ReadPort(Z80 *z80, Z80Word port)
{
return 0;
}
void ZX81WritePort(Z80 *z80, Z80Word port, Z80Byte val)
{
}
Z80Byte ZX81ReadForDisassem(Z80 *z80, Z80Word addr)
{
return mem[addr&0x7fff];
}
/* END OF FILE */
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