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/***************************************************************************
sid6526.cpp - description
-------------------
begin : Wed Jun 7 2000
copyright : (C) 2000 by Simon White
email : s_a_white@email.com
***************************************************************************/
/***************************************************************************
* *
* 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. *
* *
***************************************************************************/
/***************************************************************************
* $Log: sid6526.cpp,v $
* Revision 1.7 2002/10/02 19:48:15 s_a_white
* Make CIA control register reflect that the timer cannot be disabled.
*
* Revision 1.6 2002/03/11 18:00:29 s_a_white
* Better mirror sidplay1s handling of random numbers.
*
* Revision 1.5 2002/03/03 22:03:49 s_a_white
* Tidy.
*
* Revision 1.4 2001/10/02 18:01:36 s_a_white
* Support for cleaned c64env.
*
* Revision 1.3 2001/09/18 02:22:37 jpaana
* Fixed include filename to lowercase
*
* Revision 1.2 2001/09/03 22:24:09 s_a_white
* New counts for timer A are correctly formed.
*
* Revision 1.1 2001/09/01 11:11:19 s_a_white
* This is the old fake6526 code required for sidplay1 environment modes.
*
***************************************************************************/
#include <time.h>
#include "sidendian.h"
#include "sid6526.h"
const char * const SID6526::credit =
{ // Optional information
"*SID6526 (SIDPlay1 Fake CIA) Emulation:\0"
"\tCopyright (C) 2001 Simon White <sidplay2@email.com>\0"
};
SID6526::SID6526 (c64env *env)
:m_env(*env),
m_eventContext(m_env.context ()),
rnd(0),
m_taEvent(*this)
{
clock (0xffff);
reset ();
}
void SID6526::reset (void)
{
locked = false;
ta = ta_latch = m_count;
cra = 0;
rnd += time(NULL) & 0xff;
m_accessClk = 0;
}
uint8_t SID6526::read (uint_least8_t addr)
{
if (addr > 0x0f)
return 0;
switch (addr)
{
case 0x04:
case 0x05:
case 0x11:
case 0x12:
rnd = rnd * 13 + 1;
return (uint8_t) (rnd >> 3);
break;
default:
return regs[addr];
}
}
void SID6526::write (uint_least8_t addr, uint8_t data)
{
if (addr > 0x0f)
return;
regs[addr] = data;
if (locked)
return; // Stop program changing time interval
{ // Sync up timer
event_clock_t cycles;
cycles = m_eventContext.getTime (m_accessClk);
m_accessClk += cycles;
ta -= cycles;
}
switch (addr)
{
case 0x4: endian_16lo8 (ta_latch, data); break;
case 0x5:
endian_16hi8 (ta_latch, data);
if (!(cra & 0x01)) // Reload timer if stopped
ta = ta_latch;
break;
case 0x0e:
cra = data | 0x01;
if (data & 0x10)
{
cra &= (~0x10);
ta = ta_latch;
}
m_eventContext.schedule (&m_taEvent, (event_clock_t) ta + 1);
break;
default:
break;
}
}
void SID6526::event (void)
{ // Timer Modes
m_accessClk = m_eventContext.getTime ();
ta = ta_latch;
m_eventContext.schedule (&m_taEvent, (event_clock_t) ta + 1);
m_env.interruptIRQ (true);
}
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