/// <summary>
/// Sends a byte to the port with the specified address
/// </summary>
/// <param name="addr">Port address</param>
/// <param name="data">Data to write to the port</param>
/// <returns>Byte read from the memory</returns>
public override void OnWritePort(ushort addr, byte data)
{
// --- Handle I/O contention
base.OnWritePort(addr, data);
// --- Carry out the I/O write operation (bit 15 and bit 1 reset)
if ((addr & 0x8002) == 0)
{
// --- When paging is disabled, it will be enabled next time
// --- only after reset
if (PagingEnabled)
{
// --- Choose the RAM bank for Slot 3 (0xc000-0xffff)
_memoryDevice.PageIn(3, data & 0x07);
// --- Choose screen (Bank 5 or 7)
_memoryDevice.UseShadowScreen = ((data >> 3) & 0x01) == 0x01;
// --- Choose ROM bank for Slot 0 (0x0000-0x3fff)
_memoryDevice.SelectRom((data >> 4) & 0x01);
// --- Enable/disable paging
PagingEnabled = (data & 0x20) == 0x00;
}
}
}
/// <summary>
/// Sends a byte to the port with the specified address
/// </summary>
/// <param name="addr">Port address</param>
/// <param name="data">Data to write to the port</param>
/// <returns>Byte read from the memory</returns>
public override void WritePort(ushort addr, byte data)
{
HandleSpectrum48PortWrites(addr, data);
// --- Carry out the I/O write operation (bit 15 and bit 1 reset)
if ((addr & 0x8002) == 0)
{
// --- When paging is disabled, it will be enabled next time
// --- only after reset
if (PagingEnabled)
{
// --- Choose the RAM bank for Slot 3 (0xc000-0xffff)
MemoryDevice.PageIn(3, data & 0x07);
// --- Choose screen (Bank 5 or 7)
MemoryDevice.UseShadowScreen = ((data >> 3) & 0x01) == 0x01;
// --- Choose ROM bank for Slot 0 (0x0000-0x3fff)
MemoryDevice.SelectRom((data >> 4) & 0x01);
// --- Enable/disable paging
PagingEnabled = (data & 0x20) == 0x00;
}
}
else if (addr == 0xFFFD)
{
SoundDevice.SetRegisterIndex(data);
}
else if (addr == 0xBFFD || addr == 0xBEFD)
{
SoundDevice.SetRegisterValue(data);
}
}
/// <summary>
/// Writes the specified value to the port
/// </summary>
/// <param name="addr">Full port address</param>
/// <param name="writeValue">Value to write to the port</param>
public override void HandleWrite(ushort addr, byte writeValue)
{
// --- When paging is disabled, it will be enabled next time
// --- only after reset
if (!PagingEnabled)
{
return;
}
// --- Choose the RAM bank for Slot 3 (0xc000-0xffff)
_memoryDevice.PageIn(3, writeValue & 0x07);
// --- Choose screen (Bank 5 or 7)
_memoryDevice.UsesShadowScreen = ((writeValue >> 3) & 0x01) == 0x01;
// --- Choose ROM bank for Slot 0 (0x0000-0x3fff)
_memoryDevice.SelectRom((writeValue >> 4) & 0x01);
// --- Enable/disable paging
PagingEnabled = (writeValue & 0x20) == 0x00;
}
