add: Add bus

3 files changed, 150 insertions, 0 deletions

diff --git a/Q1.core/Components/Bus.cs b/Q1.core/Components/Bus.cs
new file mode 100644
index 0000000..02b20a7
--- /dev/null
+++ b/Q1.core/Components/Bus.cs
@@ -0,0 +1,100 @@
+namespace Q1.core.Components;
+
+using Q1.core.Arch;
+
+public class Bus : IAddressable
+{
+    private Chip? _chip;
+    private readonly List<IAddressable> _devices;
+
+    public u16 AddressableStart { get; }
+    public u16 AddressableEnd { get; }
+
+    public Bus(u16 addressableStart, u16 addressableEnd)
+    {
+        this.AddressableStart = addressableStart;
+        this.AddressableEnd = addressableEnd;
+        this._devices = new();
+    }
+
+    public void SendInterrupt(u16 code)
+    {
+        if (this._chip == null)
+            throw new InvalidOperationException("Chip is not attached to bus");
+        
+        this._chip.Interrupt(code);
+    }
+    
+    public void AttachChip(Chip chip)
+    {
+        if (this._chip != null)
+            throw new InvalidOperationException("Bus already has a chip attached.");
+
+        this._chip = chip;
+        chip.Bus = this;
+    }
+
+    public void MountDevice(IAddressable device)
+    {
+        if (device.AddressableStart >= device.AddressableEnd)
+            throw new ArgumentException("Addressable range is invalid.", nameof(device));
+
+        int index = 0;
+        while (index < this._devices.Count && this._devices[index].AddressableStart < device.AddressableStart)
+            index++;
+
+        if (index > 0)
+        {
+            IAddressable prev = this._devices[index - 1];
+            if (device.AddressableStart < prev.AddressableEnd)
+                throw new InvalidOperationException("Address range overlaps with previous device.");
+        }
+
+        if (index < this._devices.Count)
+        {
+            IAddressable next = this._devices[index];
+            if (device.AddressableEnd > next.AddressableStart)
+                throw new InvalidOperationException("Address range overlaps with next device.");
+        }
+
+        this._devices.Insert(index, device);
+    }
+
+    private IAddressable? GetDevice(u16 address)
+    {
+        foreach (IAddressable device in this._devices)
+        {
+            if (address < device.AddressableStart)
+                break;
+
+            if (address < device.AddressableEnd)
+                return device;
+        }
+
+        return null;
+    }
+
+    public u8 Read(u16 address)
+    {
+        IAddressable? device = this.GetDevice(address);
+        if (device == null)
+            return 0;
+
+        return device.Read((u16) (address - device.AddressableStart));
+    }
+
+    public void Write(u16 address, u8 value)
+    {
+        IAddressable? device = this.GetDevice(address);
+        if (device == null)
+            return;
+
+        device.Write((u16) (address - device.AddressableStart), value);
+    }
+
+    public void Clock()
+    {
+        foreach (IAddressable addressable in this._devices)
+            addressable.Clock();
+    }
+}
\ No newline at end of file
diff --git a/Q1.core/Components/IAddressable.cs b/Q1.core/Components/IAddressable.cs
new file mode 100644
index 0000000..54218d9
--- /dev/null
+++ b/Q1.core/Components/IAddressable.cs
@@ -0,0 +1,29 @@
+namespace Q1.core.Components;
+
+public interface IAddressable
+{
+    public u8 Read(u16 address);
+    public void Write(u16 address, u8 value);
+    public void Clock();
+
+    public u16 AddressableStart { get; }
+    public u16 AddressableEnd { get; }
+}
+
+public static class AddressableExtensions
+{
+    public static u16 ReadWord(this IAddressable bus, u16 address)
+    {
+        u8 high = bus.Read(address);
+        u8 low = bus.Read((u16) (address + 1));
+        return (u16) ((high << 8) | low);
+    }
+
+    public static void WriteWord(this IAddressable bus, u16 address, u16 value)
+    {
+        u8 high = (u8) (value       & 0xFF);
+        u8 low = (u8) ((value >> 8) & 0xFF);
+        bus.Write(address, low);
+        bus.Write((u16) (address + 1), high);
+    }
+}
\ No newline at end of file
diff --git a/Q1.core/Components/Memory.cs b/Q1.core/Components/Memory.cs
new file mode 100644
index 0000000..9d23c7a
--- /dev/null
+++ b/Q1.core/Components/Memory.cs
@@ -0,0 +1,21 @@
+namespace Q1.core.Components;
+
+public class Memory : IAddressable
+{
+    private readonly u8[] _memory;
+    
+    public u16 AddressableStart { get; }
+    public u16 AddressableEnd { get; }
+    
+    public Memory(u16 start, u16 size)
+    {
+        this.AddressableStart = start;
+        this.AddressableEnd = (u16) (start + size);
+        
+        this._memory = new u8[size];
+    }
+    
+    public u8 Read(u16 address) => this._memory[address];
+    public void Write(u16 address, u8 value) => this._memory[address] = value;
+    public void Clock() { /* No timing behavior for simple memory */ }
+}
\ No newline at end of file