zxemu.c

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/* Xep128: Minimalistic Enterprise-128 emulator with focus on "exotic" hardware
   Copyright (C)2015,2016 LGB (Gábor Lénárt) <lgblgblgb@gmail.com>
   http://xep128.lgb.hu/
 
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 */
 
#include "xep128.h"
#include "zxemu.h"
#include "cpu.h"
#include "primoemu.h"
 
 
 
int zxemu_on = 0;
 
 
 
 
void zxemu_switch ( Uint8 data )
{
        data &= 128;
        if (data == zxemu_on)
                return;
        zxemu_on = data;
        DEBUG("ZXEMU: emulation is turned %s." NL, zxemu_on ? "ON" : "OFF");
        if (zxemu_on)
                primo_switch(0);
        nmi_pending = 0;
}
 
 
static int zxemu_nmi ( void )
{
        nmi_pending = zxemu_on;
        return nmi_pending;
}
 
 
void zxemu_write_ula ( Uint8 hiaddr, Uint8 data )
{
        ports[0x40] = hiaddr;   // high I/O address
        ports[0x41] = 0xFE;             // low I/O address, the ULA port
        ports[0x42] = data;             // data on the bus
        ports[0x43] = 0;                // ?? 0 = I/O kind of op
        if (!zxemu_nmi())
                DEBUG("ZXEMU: ULA write: no NMI (switched off)" NL);
        DEBUG("ZXEMU: writing ULA at %04Xh (data: %02Xh)" NL, Z80_PC, data);
}
 
 
Uint8 zxemu_read_ula ( Uint8 hiaddr )
{
        ports[0x40] = hiaddr;
        ports[0x41] = 0xFE;
        ports[0x42] = 0xFF; // ???????
        ports[0x43] = 0;
        if (!zxemu_nmi())
                DEBUG("ZXEMU: ULA read: no NMI (switched off)" NL);
        DEBUG("ZXEMU: reading ULA at %04Xh" NL, Z80_PC);
        return zxemu_on ? 0xBF : 0xFF;
}
 
 
/* This function is only allowed to be called, if zxemu_on is non-zero, and attribute area is written! */
void zxemu_attribute_memory_write ( Uint16 address, Uint8 data )
{
        ports[0x40] = address >> 8;
        ports[0x41] = address & 0xFF;
        ports[0x42] = data;
        ports[0x43] = 0x80;
        zxemu_nmi();
        DEBUG("ZXEMU: attrib-mem trap at %04Xh" NL, address);
}