public byte Read(int address)
{
// Special behavior for when the Ms. Pac-Man daughterboard is enabled.
if (_auxBoardEnabled)
{
if (address <= 0x4000)
{
// For all original ROM areas, read our patched version.
return(_auxBoard.AuxROMs[address]);
}
else if (address >= 0x8000 && address < 0x8800)
{
// Aux ROM U5
return(_auxBoard.AuxROMs[address - 0x8000 + 0x6000]);
}
else if (address >= 0x8800 && address < 0xA000)
{
// Aux ROM U6
return(_auxBoard.AuxROMs[(address & 0xFFF) + 0x5000]);
}
// else fall through to original memory read behaviors.
}
if (address >= 0x0000 && address <= 0x4FFF)
{
// Includes ROM, Video RAM, RAM, and sprites.
return(_memory[address]);
}
else if (address >= 0x5000 && address <= 0x503F)
{
// IN0 (player 1 joystick, credit switches, and rack advance button) (each byte returns same value).
return(ButtonState.GetPortIN0());
}
else if (address == 0x5003)
{
// Flip screen (bit 0: 0 = normal, 1 = flipped)
return((byte)(_flipScreen == true ? 1 : 0));
}
else if (address == 0x5004)
{
// 1 player start lamp (bit 0: 0 = on, 1 = off)
// I don't believe the Pac-Man arcade cabinet had support for blinking start buttons.
// Other games on the same platform might though.
return(0x01);
}
else if (address == 0x5005)
{
// 2 player start lamp (bit 0: 0 = on, 1 = off)
// I don't believe the Pac-Man arcade cabinet had support for blinking start buttons.
// Other games on the same platform might though.
return(0x01);
}
else if (address == 0x5006)
{
// Coin lockout (bit 0: 0 = unlocked, 1 = locked)
// I don't believe the Pac-Man arcade cabinet had a coin lockout mechanism.
return(0x00);
}
else if (address == 0x5007)
{
// Coin counter (trigger by changing bit 0 from 0 to 1)
return(0x00);
}
else if (address >= 0x5040 && address <= 0x507F)
{
// IN1 (player 2 joystick, start buttons, board test and cabinet mode switches) (each byte returns same value).
// Note that bit 7 is the cabinet mode setting which comes from a DIP switch.
var cabinetMode = (byte)((DIPSwitchState.CabinetMode == CabinetMode.Upright ? 1 : 0) << 7);
return((byte)(ButtonState.GetPortIN1() | cabinetMode));
}
else if (address >= 0x5080 && address <= 0x50BF)
{
// Dip Switch Settings (each byte returns same value).
return(DIPSwitchState.GetByte());
}
else if (address < 0x00)
{
throw new IndexOutOfRangeException(String.Format("Invalid read memory address (< 0x0000): 0x{0:X4}", address));
}
else
{
// TODO: I may need to remove and/or relax this restriction. Adding an exception for now
// so I can troubleshoot while getting things running.
throw new Exception(String.Format("Unexpected read memory address: 0x{0:X4}", address));
}
}