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Cleaned up the RIOT class a little more, hopefully making it easier to 

understand.  Eliminated certains constants that I could never really
explain (like the 0x40000 constant from z26), and more properly emulated
the behaviour when going negative on the timer count (according to the
documentation).


git-svn-id: svn://svn.code.sf.net/p/stella/code/trunk@1483 8b62c5a3-ac7e-4cc8-8f21-d9a121418aba
This commit is contained in:
stephena 2008-04-23 16:51:11 +00:00
parent 0682a85999
commit 74362c3f0f
2 changed files with 110 additions and 137 deletions
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158
stella/src/emucore/M6532.cxx
View File

@ -13,7 +13,7 @@
// See the file "license" for information on usage and redistribution of
// this file, and for a DISCLAIMER OF ALL WARRANTIES.
//
// $Id: M6532.cxx,v 1.20 2008-04-20 19:52:33 stephena Exp $
// $Id: M6532.cxx,v 1.21 2008-04-23 16:51:11 stephena Exp $
//============================================================================
#include <assert.h>
@ -55,15 +55,14 @@ void M6532::reset()
myTimer = 25 + (random.next() % 75);
myIntervalShift = 6;
myCyclesWhenTimerSet = 0;
myTimerReadAfterInterrupt = false;
myInterruptEnabled = false;
myInterruptTriggered = false;
// Zero the I/O registers
myOutA = 0x00;
myDDRA = 0x00;
myDDRB = 0x00;
myDDRA = myDDRB = myOutA = 0x00;
// Zero the timer registers
myOutTimer[0] = myOutTimer[1] = myOutTimer[2] = myOutTimer[3] = 0x0;
myOutTimer[0] = myOutTimer[1] = myOutTimer[2] = myOutTimer[3] = 0x00;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@ -161,30 +160,26 @@ uInt8 M6532::peek(uInt16 addr)
case 0x04: // Timer Output
case 0x06:
{
uInt32 timer = timerClocks();
myInterruptTriggered = false;
Int32 timer = timerClocks();
// See if the timer has expired yet?
// Note that this constant comes from z26, and corresponds to
// 256 intervals of T1024T (ie, the maximum that the timer
// should hold)
if(!(timer & 0x40000))
if(timer >= 0)
{
return (timer >> myIntervalShift) & 0xff;
return (uInt8)(timer >> myIntervalShift);
}
else
{
myTimerReadAfterInterrupt = true;
return timer & 0xff;
if(timer != -1)
myInterruptTriggered = true;
return (uInt8)(timer >= -256 ? timer : 0);
}
}
case 0x05: // Interrupt Flag
case 0x07:
{
// TODO - test this
// it seems as if myTimerReadAfterInterrupt being true
// would mean that the interrupt has been enabled??
if((timerClocks() >= 0) || myTimerReadAfterInterrupt)
if((timerClocks() >= 0) || myInterruptEnabled && myInterruptTriggered)
return 0x00;
else
return 0x80;
@ -210,8 +205,23 @@ void M6532::poke(uInt16 addr, uInt8 value)
if((addr & 0x1080) == 0x0080 && (addr & 0x0200) == 0x0000)
{
myRAM[addr & 0x007f] = value;
return;
}
else if((addr & 0x07) == 0x00) // Port A I/O Register (Joystick)
// A2 Distingusishes I/O registers from the timer
if((addr & 0x04) != 0)
{
if((addr & 0x10) != 0)
{
myInterruptEnabled = (addr & 0x08);
setTimerRegister(value, addr & 0x03);
}
}
else
{
switch(addr & 0x03)
{
case 0: // Port A I/O Register (Joystick)
{
myOutA = value;
uInt8 a = myOutA & myDDRA;
@ -227,35 +237,29 @@ void M6532::poke(uInt16 addr, uInt8 value)
port1.write(Controller::Two, a & 0x02);
port1.write(Controller::Three, a & 0x04);
port1.write(Controller::Four, a & 0x08);
break;
}
else if((addr & 0x07) == 0x01) // Port A Data Direction Register
case 1: // Port A Data Direction Register
{
myDDRA = value;
uInt8 a = myOutA | ~myDDRA;
// TODO - Fix this properly in the core
// Any time the core code needs to know what type of controller
// is connected, it's by definition a bug
// A real Atari doesn't 'know' that an AVox is connected, so we
// shouldn't either
/*
20060608 bkw: Not the most elegant thing in the world...
Undocumented feature used by the AtariVox and SaveKey.
When the DDR is changed, the ORA (output register A) cached
from a previous write to SWCHA is 'applied' to the controller pins.
When a bit in the DDR is set as input, +5V is placed on its output
pin. When it's set as output, either +5V or 0V (depending on the
contents of SWCHA) will be placed on the output pin.
The standard macros for the AtariVox use this fact to send data
to the port.
to the port. This is represented by the following algorithm:
This code isn't 100% correct: it assumes the SWCHA bits are all 0.
This is good enough to emulate the AtariVox, if the programmer is
using SWACNT to do output (e.g. the SPKOUT macro from speakjet.inc)
and if he's leaving SWCHA alone.
The inaccuracy here means that wrongly-written code will still
be able to drive the emulated AtariVox, even though it wouldn't
work on real hardware.
if(DDR bit is input) set output as 1
else if(DDR bit is output) set output as bit in ORA
*/
uInt8 a = myOutA | ~myDDRA;
Controller& port0 = myConsole.controller(Controller::Left);
port0.write(Controller::One, a & 0x10);
port0.write(Controller::Two, a & 0x20);
@ -267,63 +271,25 @@ void M6532::poke(uInt16 addr, uInt8 value)
port1.write(Controller::Two, a & 0x02);
port1.write(Controller::Three, a & 0x04);
port1.write(Controller::Four, a & 0x08);
break;
}
else if((addr & 0x07) == 0x02) // Port B I/O Register (Console switches)
{
return; // hardwired as read-only
default: // Port B I/O & DDR Registers (Console switches)
break; // hardwired as read-only
}
else if((addr & 0x07) == 0x03) // Port B Data Direction Register
{
return; // hardwired as read-only
}
else if((addr & 0x17) == 0x14) // Write timer divide by 1
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void M6532::setTimerRegister(uInt8 value, uInt8 interval)
{
myOutTimer[0] = value;
myIntervalShift = 0;
myTimer = myOutTimer[0] << myIntervalShift;
static const uInt8 shift[] = { 0, 3, 6, 10 };
myInterruptTriggered = false;
myIntervalShift = shift[interval];
myOutTimer[interval] = value;
myTimer = value << myIntervalShift;
myCyclesWhenTimerSet = mySystem->cycles();
myTimerReadAfterInterrupt = false;
}
else if((addr & 0x17) == 0x15) // Write timer divide by 8
{
myOutTimer[1] = value;
myIntervalShift = 3;
myTimer = myOutTimer[1] << myIntervalShift;
myCyclesWhenTimerSet = mySystem->cycles();
myTimerReadAfterInterrupt = false;
}
else if((addr & 0x17) == 0x16) // Write timer divide by 64
{
myOutTimer[2] = value;
myIntervalShift = 6;
myTimer = myOutTimer[2] << myIntervalShift;
myCyclesWhenTimerSet = mySystem->cycles();
myTimerReadAfterInterrupt = false;
}
else if((addr & 0x17) == 0x17) // Write timer divide by 1024
{
myOutTimer[3] = value;
myIntervalShift = 10;
myTimer = myOutTimer[3] << myIntervalShift;
myCyclesWhenTimerSet = mySystem->cycles();
myTimerReadAfterInterrupt = false;
}
else if((addr & 0x14) == 0x04) // Write Edge Detect Control
{
#ifdef DEBUG_ACCESSES
cerr << "M6532 Poke (Write Edge Detect): "
<< ((addr & 0x02) ? "PA7 enabled" : "PA7 disabled")
<< ", "
<< ((addr & 0x01) ? "Positive edge" : "Negative edge")
<< endl;
#endif
}
else
{
#ifdef DEBUG_ACCESSES
cerr << "BAD M6532 Poke: " << hex << addr << endl;
#endif
}
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@ -343,10 +309,12 @@ bool M6532::save(Serializer& out) const
out.putInt(myTimer);
out.putInt(myIntervalShift);
out.putInt(myCyclesWhenTimerSet);
out.putBool(myTimerReadAfterInterrupt);
out.putByte((char)myOutA);
out.putBool(myInterruptEnabled);
out.putBool(myInterruptTriggered);
out.putByte((char)myDDRA);
out.putByte((char)myDDRB);
out.putByte((char)myOutA);
out.putByte((char)myOutTimer[0]);
out.putByte((char)myOutTimer[1]);
out.putByte((char)myOutTimer[2]);
@ -384,12 +352,12 @@ bool M6532::load(Deserializer& in)
myTimer = (uInt32) in.getInt();
myIntervalShift = (uInt32) in.getInt();
myCyclesWhenTimerSet = (uInt32) in.getInt();
myTimerReadAfterInterrupt = in.getBool();
myInterruptEnabled = in.getBool();
myInterruptTriggered = in.getBool();
myOutA = (uInt8) in.getByte();
myDDRA = (uInt8) in.getByte();
myDDRB = (uInt8) in.getByte();
myOutA = (uInt8) in.getByte();
myOutTimer[0] = (uInt8) in.getByte();
myOutTimer[1] = (uInt8) in.getByte();
myOutTimer[2] = (uInt8) in.getByte();

17
stella/src/emucore/M6532.hxx
View File

@ -13,7 +13,7 @@
// See the file "license" for information on usage and redistribution of
// this file, and for a DISCLAIMER OF ALL WARRANTIES.
//
// $Id: M6532.hxx,v 1.11 2008-04-20 19:52:33 stephena Exp $
// $Id: M6532.hxx,v 1.12 2008-04-23 16:51:11 stephena Exp $
//============================================================================
#ifndef M6532_HXX
@ -32,7 +32,7 @@ class Deserializer;
RIOT
@author Bradford W. Mott
@version $Id: M6532.hxx,v 1.11 2008-04-20 19:52:33 stephena Exp $
@version $Id: M6532.hxx,v 1.12 2008-04-23 16:51:11 stephena Exp $
*/
class M6532 : public Device
{
@ -130,6 +130,8 @@ class M6532 : public Device
inline Int32 timerClocks()
{ return myTimer - (mySystem->cycles() - myCyclesWhenTimerSet); }
void setTimerRegister(uInt8 data, uInt8 interval);
private:
// Reference to the console
const Console& myConsole;
@ -146,11 +148,11 @@ class M6532 : public Device
// Indicates the number of cycles when the timer was last set
Int32 myCyclesWhenTimerSet;
// Indicates if a read from timer has taken place after interrupt occured
bool myTimerReadAfterInterrupt;
// Indicates if a timer interrupt has been enabled
bool myInterruptEnabled;
// Last value written to Port A
uInt8 myOutA;
// Indicates if a read from timer has taken place after interrupt occured
bool myInterruptTriggered;
// Data Direction Register for Port A
uInt8 myDDRA;
@ -158,6 +160,9 @@ class M6532 : public Device
// Data Direction Register for Port B
uInt8 myDDRB;
// Last value written to Port A
uInt8 myOutA;
// Last value written to the timer registers
uInt8 myOutTimer[4];