/// <summary>
/// Reads the memory at the specified address
/// </summary>
/// <param name="addr">Memory address</param>
/// <param name="noContention">Indicates non-contended read operation</param>
/// <returns>Byte read from the memory</returns>
public override byte Read(ushort addr, bool noContention = false)
{
var memIndex = addr & 0x3FFF;
byte memValue;
switch (addr & 0xC000)
{
case 0x0000:
return(CurrentRomPage[memIndex]);
case 0x4000:
memValue = RamBanks[5][memIndex];
if (noContention || _screenDevice == null)
{
return(memValue);
}
_cpu?.Delay(_screenDevice.GetContentionValue(HostVm.CurrentFrameTact));
return(memValue);
case 0x8000:
return(RamBanks[2][memIndex]);
default:
memValue = RamBanks[_currentSlot3Bank][memIndex];
if ((_currentSlot3Bank & 0x01) == 0)
{
return(memValue);
}
// --- Bank 1, 3, 5, and 7 are contended
_cpu?.Delay(_screenDevice.GetContentionValue(HostVm.CurrentFrameTact));
return(memValue);
}
}
/// <summary>
/// Reads the memory at the specified address
/// </summary>
/// <param name="addr">Memory address</param>
/// <returns>Byte read from the memory</returns>
public byte Read(ushort addr)
{
var memIndex = addr & 0x3FFF;
switch (addr & 0xC000)
{
case 0x0000:
return(_currentRomPage[memIndex]);
case 0x4000:
if (_screenDevice != null)
{
_cpu?.Delay(_screenDevice.GetContentionValue(HostVm.CurrentFrameTact));
}
return(_ramBanks[5][memIndex]);
case 0x8000:
return(_ramBanks[2][memIndex]);
default:
if ((_currentSlot3Bank & 0x01) != 0)
{
// --- Bank 1, 3, 5, and 7 are contended
_cpu?.Delay(_screenDevice.GetContentionValue(HostVm.CurrentFrameTact));
}
return(_ramBanks[_currentSlot3Bank][memIndex]);
}
}
/// <summary>
/// Reads the memory at the specified address
/// </summary>
/// <param name="addr">Memory address</param>
/// <returns>Byte read from the memory</returns>
public byte Read(ushort addr)
{
var value = _memory[addr];
if ((addr & 0xC000) == 0x4000)
{
_cpu.Delay(_screenDevice.GetContentionValue(HostVm.CurrentFrameTact));
}
return(value);
}
/// <summary>
/// Emulates memory contention
/// </summary>
/// <param name="addr">Contention address</param>
public virtual void ContentionWait(ushort addr)
{
if ((addr & 0xC000) == 0x4000)
{
var delay = ScreenDevice.GetContentionValue(HostVm.CurrentFrameTact);
Cpu?.Delay(delay);
}
}
/// <summary>
/// Reads the port with the specified address
/// </summary>
/// <param name="addr">Port address</param>
/// <returns>Byte read from the port</returns>
public virtual byte OnReadPort(ushort addr)
{
// --- Apply I/O contention delay
var lowBit = (addr & 0x0001) != 0;
var ulaHigh = (addr & 0xc000) == 0x4000;
if (ulaHigh)
{
Cpu.Delay(ScreenDevice.GetContentionValue(HostVm.CurrentFrameTact - 1));
}
else
{
if (!lowBit)
{
Cpu.Delay(ScreenDevice.GetContentionValue(HostVm.CurrentFrameTact));
}
}
return(0xFF);
}
/// <summary>
/// Applies the delay according to the current frame tact
/// </summary>
protected void ApplyDelay()
{
if (HostVm == null)
{
return;
}
var delay = ScreenDevice.GetContentionValue(HostVm.CurrentFrameTact);
Cpu.Delay(delay);
HostVm.ContentionAccumulated += delay;
}
/// <summary>
/// Reads the memory at the specified address
/// </summary>
/// <param name="addr">Memory address</param>
/// <param name="noContention">Indicates non-contended read operation</param>
/// <returns>Byte read from the memory</returns>
public override byte Read(ushort addr, bool noContention = false)
{
var memIndex = addr & 0x3FFF;
byte memValue;
switch (addr & 0xC000)
{
case 0x0000:
return(SpecialMode
? RamBanks[_slots[0]][memIndex]
: CurrentRomPage[memIndex]);
case 0x4000:
memValue = RamBanks[_slots[1]][memIndex];
if (noContention || _screenDevice == null)
{
return(memValue);
}
_cpu?.Delay(_screenDevice.GetContentionValue(HostVm.CurrentFrameTact));
return(memValue);
case 0x8000:
return(RamBanks[_slots[2]][memIndex]);
default:
var bankIndex = _slots[3];
memValue = RamBanks[bankIndex][memIndex];
if (bankIndex < 4)
{
return(memValue);
}
// --- Bank 4, 5, 6, and 7 are contended
_cpu?.Delay(_screenDevice.GetContentionValue(HostVm.CurrentFrameTact));
return(memValue);
}
}
/// <summary>
/// Emulates I/O contention
/// </summary>
/// <param name="addr">Contention address</param>
public void ContentionWait(ushort addr)
{
Cpu.Delay(4);
}
/// <summary>
/// Emulates I/O contention
/// </summary>
/// <param name="addr">Contention address</param>
public virtual void ContentionWait(ushort addr)
{
var lowBit = (addr & 0x0001) != 0;
if ((addr & 0xc000) == 0x4000 ||
(addr & 0xc000) == 0xC000 && IsContendedBankPagedIn())
{
if (lowBit)
{
// --- C:1 x 4 contention scheme
Cpu.Delay(ScreenDevice.GetContentionValue(HostVm.CurrentFrameTact));
Cpu.Delay(1);
Cpu.Delay(ScreenDevice.GetContentionValue(HostVm.CurrentFrameTact));
Cpu.Delay(1);
Cpu.Delay(ScreenDevice.GetContentionValue(HostVm.CurrentFrameTact));
Cpu.Delay(1);
Cpu.Delay(ScreenDevice.GetContentionValue(HostVm.CurrentFrameTact));
Cpu.Delay(1);
}
else
{
// --- C:1, C:3 contention scheme
Cpu.Delay(ScreenDevice.GetContentionValue(HostVm.CurrentFrameTact));
Cpu.Delay(1);
Cpu.Delay(ScreenDevice.GetContentionValue(HostVm.CurrentFrameTact));
Cpu.Delay(3);
}
}
else
{
if (lowBit)
{
// --- N:4 contention scheme
Cpu.Delay(4);
}
else
{
// --- N:1, C:3 contention scheme
Cpu.Delay(1);
Cpu.Delay(ScreenDevice.GetContentionValue(HostVm.CurrentFrameTact));
Cpu.Delay(3);
}
}
}