napple1/src/pia6820.c
2023-06-07 15:17:25 +09:00

105 lines
1.9 KiB
C

/* napple1 ncurses Apple 1 emulator
* Copyright (C) 2008 Nobu Hatano
*
* Pom1 Apple 1 Emulator
* Copyright (C) 2000 Verhille Arnaud
* Copyright (C) 2006 John D. Corrado
*
* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include "pia6820.h"
#include "screen.h"
static unsigned char _dspCr = 0, _dsp = 0, _kbdCr = 0, _kbd = 0;
static int kbdInterrups = 0, dspOutput = 0;
void resetPia6820(void)
{
kbdInterrups = dspOutput = 0;
_kbdCr = _dspCr = 0;
}
void setKdbInterrups(int b)
{
kbdInterrups = b;
}
int getKbdInterrups(void)
{
return kbdInterrups;
}
int getDspOutput(void)
{
return dspOutput;
}
void writeDspCr(unsigned char dspCr)
{
if (!dspOutput && dspCr >= 0x80)
dspOutput = 1;
else
_dspCr = dspCr;
}
void writeDsp(unsigned char dsp)
{
if (dsp >= 0x80)
dsp -= 0x80;
outputDsp(dsp);
_dsp = dsp;
}
void writeKbdCr(unsigned char kbdCr)
{
if (!kbdInterrups && kbdCr >= 0x80)
kbdInterrups = 1;
else
_kbdCr = kbdCr;
}
void writeKbd(unsigned char kbd)
{
_kbd = kbd;
}
unsigned char readDspCr(void)
{
return _dspCr;
}
unsigned char readDsp(void)
{
return _dsp;
}
unsigned char readKbdCr(void)
{
if (kbdInterrups && _kbdCr >= 0x80)
{
_kbdCr = 0;
return 0xA7;
}
return _kbdCr;
}
unsigned char readKbd(void)
{
return _kbd;
}