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ZXHawk: Small change to 128 paging

This commit is contained in:
Asnivor 2018-03-26 16:47:04 +01:00
parent f016c60b13
commit e8cd3b259c
1 changed files with 31 additions and 115 deletions
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146
BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ZXSpectrum128K/ZX128.Port.cs
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@ -74,71 +74,6 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
}
}
/*
// Check whether the low bit is reset
// Technically the ULA should respond to every even I/O address
bool lowBitReset = (port & 0x0001) == 0;
// Kempston joystick input takes priority over all other input
// if this is detected just return the kempston byte
if ((port & 0xe0) == 0 || (port & 0x20) == 0)
{
if (LocateUniqueJoystick(JoystickType.Kempston) != null)
return (byte)((KempstonJoystick)LocateUniqueJoystick(JoystickType.Kempston) as KempstonJoystick).JoyLine;
InputRead = true;
}
else if (lowBitReset)
{
// Even I/O address so get input from keyboard
KeyboardDevice.ReadPort(port, ref result);
// not a lagframe
InputRead = true;
// tape loading monitor cycle
TapeDevice.MonitorRead();
// process tape INs
TapeDevice.ReadPort(port, ref result);
}
else if ((port & 0xc002) == 0xc000)
{
// AY sound chip
result = (int)AYDevice.PortRead();
}
else
{
// devices other than the ULA will respond here
// Kempston Mouse (not implemented yet)
// If this is an unused port the floating memory bus should be returned
// Floating bus is read on the previous cycle
int _tStates = CurrentFrameCycle - 1;
// if we are on the top or bottom border return 0xff
if ((_tStates < ULADevice.contentionStartPeriod) || (_tStates > ULADevice.contentionEndPeriod))
{
result = 0xff;
}
else
{
if (ULADevice.floatingBusTable[_tStates] < 0)
{
result = 0xff;
}
else
{
result = ReadBus((ushort)ULADevice.floatingBusTable[_tStates]);
}
}
}
*/
return (byte)result;
}
@ -157,47 +92,45 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
// get a BitArray of the value byte
BitArray bits = new BitArray(new byte[] { value });
long currT = CPU.TotalExecutedCycles;
// handle AY port writes
AYDevice.WritePort(port, value);
// paging
if (port == 0x7ffd)
// memory paging
// this is controlled by writes to port 0x7ffd
// but it is only partially decoded so it actually responds to any port with bits 1 and 15 reset
if (portBits[1] == false && portBits[15] == false)
{
//if (PagingDisabled)
//return;
// Bits 0, 1, 2 select the RAM page
var rp = value & 0x07;
if (rp < 8)
RAMPaged = rp;
// bit 3 controls shadow screen
SHADOWPaged = bits[3];
if (SHADOWPaged == false)
// if paging is disabled then all writes to this port are ignored until the next reboot
if (!PagingDisabled)
{
// Bits 0, 1, 2 select the RAM page
var rp = value & 0x07;
if (RAMPaged != rp && rp < 8)
RAMPaged = rp;
// bit 3 controls shadow screen
if (SHADOWPaged != bits[3])
SHADOWPaged = bits[3];
// ROM page
if (bits[4])
{
// 48k basic rom
ROMPaged = 1;
}
else
{
// 128k editor and menu system
ROMPaged = 0;
}
// Bit 5 set signifies that paging is disabled until next reboot
PagingDisabled = bits[5];
}
else
{
// no changes to paging
}
// ROM page
if (bits[4])
{
// 48k basic rom
ROMPaged = 1;
}
else
{
// 128k editor and menu system
ROMPaged = 0;
}
// Bit 5 set signifies that paging is disabled until next reboot
PagingDisabled = bits[5];
}
// Check whether the low bit is reset
@ -229,25 +162,8 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
TapeDevice.WritePort(port, value);
// Tape
//TapeDevice.ProcessMicBit((value & MIC_BIT) != 0);
}
/*
// Active AY Register
if ((port & 0xc002) == 0xc000)
{
var reg = value & 0x0f;
AYDevice.SelectedRegister = reg;
CPU.TotalExecutedCycles += 3;
}
// AY Write
if ((port & 0xc002) == 0x8000)
{
AYDevice.PortWrite(value);
CPU.TotalExecutedCycles += 3;
//TapeDevice.ProcessMicBit((value & MIC_BIT) != 0);
}
*/
}
}
}