public void ReadHighByteOnly(byte channel)
{
Reset();
mbbsEmuCpuRegisters.AL = (byte)((2 << 4) | (channel << 6));
fakeClock.CurrentTick = 0.25;
var expected = (ushort)(int)(ProgrammableIntervalTimer.FREQUENCY * (1.0 - fakeClock.CurrentTick));
var instructions = new Assembler(16);
instructions.@out(0x43, al);
instructions.@in(al, (byte)(0x40 + channel));
instructions.mov(ah, al);
instructions.@in(al, (byte)(0x40 + channel));
instructions.hlt();
CreateCodeSegment(instructions);
while (!mbbsEmuCpuRegisters.Halt)
{
mbbsEmuCpuCore.Tick();
}
mbbsEmuCpuRegisters.AL.Should().Be((byte)(expected >> 8));
mbbsEmuCpuRegisters.AH.Should().Be((byte)(expected >> 8));
}
public void ReadLatchedValue(byte channel)
{
Reset();
mbbsEmuCpuRegisters.AL = (byte)((0 << 4) | (channel << 6)); // latched
fakeClock.CurrentTick = 0.25;
var expected = (ushort)(int)(ProgrammableIntervalTimer.FREQUENCY * (1.0 - fakeClock.CurrentTick));
var instructions = new Assembler(16);
instructions.@out(0x43, al);
instructions.@in(al, (byte)(0x40 + channel));
instructions.mov(ah, al);
instructions.@in(al, (byte)(0x40 + channel));
instructions.xchg(ah, al);
instructions.hlt();
CreateCodeSegment(instructions);
// program the PIT - sets the latched value
mbbsEmuCpuCore.Tick();
// reset clock to another value to verify latched value is read
// and not this new value
fakeClock.CurrentTick = 0;
while (!mbbsEmuCpuRegisters.Halt)
{
mbbsEmuCpuCore.Tick();
}
mbbsEmuCpuRegisters.AL.Should().Be((byte)expected);
mbbsEmuCpuRegisters.AH.Should().Be((byte)(expected >> 8));
}