Fixed bug in carry flag on SUB operations; SUBLZ X,X now works correctly. Alto now appears to boot successfully. Skeleton of Display hardware added.

Contralto/AltoSystem.cs

@@ -7,6 +7,7 @@ using System.Threading.Tasks;
 using Contralto.CPU;
 using Contralto.IO;
 using Contralto.Memory;
+using Contralto.Display;
 
 namespace Contralto
 {
@@ -23,6 +24,7 @@ namespace Contralto
             _mem = new Memory.Memory();
             _keyboard = new Keyboard();
             _diskController = new DiskController(this);
+            _displayController = new DisplayController(this);
 
             // Attach memory-mapped devices to the bus
             _memBus.AddDevice(_mem);
@@ -32,7 +34,8 @@ namespace Contralto
             _clockableDevices = new List<IClockable>();
             _clockableDevices.Add(_memBus);
             _clockableDevices.Add(_diskController);
-            _clockableDevices.Add(_cpu);
+            _clockableDevices.Add(_displayController);
+            _clockableDevices.Add(_cpu);            
 
             Reset();
         }
@@ -45,6 +48,7 @@ namespace Contralto
             ALU.Reset();
             Shifter.Reset();
             _diskController.Reset();
+            _displayController.Reset();
         }
 
         public void SingleStep()
@@ -85,6 +89,7 @@ namespace Contralto
         private Contralto.Memory.Memory _mem;
         private Keyboard _keyboard;
         private DiskController _diskController;
+        private DisplayController _displayController;
 
         private List<IClockable> _clockableDevices;
     }

Contralto/CPU/ALU.cs

@@ -72,7 +72,7 @@ namespace Contralto.CPU
                     //  addition (1s complement), a carry out means borrow; thus,
                     //  a carry is generated when there is no underflow and no carry
                     //  is generated when there is underflow."
-                    _carry = (r <= 0) ? 0 : 1;
+                    _carry = (r < 0) ? 0 : 1;
                     break;
 
                 case AluFunction.BusPlusT:
@@ -82,12 +82,12 @@ namespace Contralto.CPU
 
                 case AluFunction.BusMinusT:
                     r = bus - t;
-                    _carry = (r <= 0) ? 0 : 1;
+                    _carry = (r < 0) ? 0 : 1;
                     break;
 
                 case AluFunction.BusMinusTMinus1:
                     r = bus - t - 1;
-                    _carry = (r <= 0) ? 0 : 1;
+                    _carry = (r < 0) ? 0 : 1;
                     break;
 
                 case AluFunction.BusPlusTPlus1:

Contralto/CPU/CPU.cs

@@ -31,6 +31,7 @@ namespace Contralto.CPU
             _tasks[(int)TaskType.Emulator] = new EmulatorTask(this);
             _tasks[(int)TaskType.DiskSector] = new DiskTask(this, true);
             _tasks[(int)TaskType.DiskWord] = new DiskTask(this, false);
+            _tasks[(int)TaskType.DisplayWord] = new DisplayWordTask(this);
 
             Reset();
         }

Contralto/CPU/MicroInstruction.cs

@@ -135,6 +135,22 @@ namespace Contralto.CPU
         ReadKDATA = 4,
     }
 
+    enum DisplayWordF2
+    {
+        LoadDDR = 8,
+    }
+
+    enum DisplayHorizontalF2
+    {
+        EVENFIELD = 8,
+        SETMODE = 9,
+    }
+
+    enum DisplayVerticalF2
+    {
+        EVENFIELD = 8,
+    }
+
     public class MicroInstruction
     {
         public MicroInstruction(UInt32 code)

Contralto/CPU/Shifter.cs

@@ -143,6 +143,11 @@ namespace Contralto.CPU
                         // "...and places the low order bit of T into the high order bit position 
                         // of the shifter output on right shifts."
                         _output |= (ushort)((t & 0x1) << 15);
+
+                        if (_count != 1)
+                        {
+                            throw new NotImplementedException("magic LCY 8 not implemented yet.");
+                        }
                     }
                     else if (_dns)
                     {

Contralto/CPU/Tasks/DisplayHorizontalTask.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+using Contralto.Memory;
+
+namespace Contralto.CPU
+{
+    public partial class AltoCPU
+    {
+        /// <summary>
+        /// DisplayWordTask provides functionality for the DWT task
+        /// </summary>
+        private class DisplayHorizontalTask : Task
+        {
+            public DisplayHorizontalTask(AltoCPU cpu) : base(cpu)
+            {
+                _taskType = TaskType.DisplayHorizontal;
+
+                // The Wakeup signal is always true for the Emulator task.
+                _wakeup = false;
+            }            
+            
+            protected override void ExecuteSpecialFunction2(MicroInstruction instruction)
+            {
+                DisplayWordF2 ef2 = (DisplayWordF2)instruction.F2;
+                switch (ef2)
+                {
+                    case DisplayWordF2.LoadDDR:
+
+                        break;
+
+                    default:
+                        throw new InvalidOperationException(String.Format("Unhandled display word F2 {0}.", ef2));
+                        break;
+                }
+            }
+        }
+    }
+}

Contralto/CPU/Tasks/DisplayWordTask.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+using Contralto.Memory;
+
+namespace Contralto.CPU
+{
+    public partial class AltoCPU
+    {
+        /// <summary>
+        /// DisplayWordTask provides functionality for the DWT task
+        /// </summary>
+        private class DisplayWordTask : Task
+        {
+            public DisplayWordTask(AltoCPU cpu) : base(cpu)
+            {
+                _taskType = TaskType.DisplayWord;
+
+                // The Wakeup signal is always true for the Emulator task.
+                _wakeup = false;
+            }            
+            
+            protected override void ExecuteSpecialFunction2(MicroInstruction instruction)
+            {
+                DisplayWordF2 ef2 = (DisplayWordF2)instruction.F2;
+                switch (ef2)
+                {
+                    case DisplayWordF2.LoadDDR:
+
+                        break;
+
+                    default:
+                        throw new InvalidOperationException(String.Format("Unhandled display word F2 {0}.", ef2));
+                        break;
+                }
+            }
+        }
+    }
+}

Contralto/CPU/Tasks/EmulatorTask.cs

@@ -76,8 +76,9 @@ namespace Contralto.CPU
                         break;
 
                     case EmulatorF1.STARTF:
-                        // Dispatch function to I/O based on contents of AC0... (TBD: what are these?)
-                        throw new NotImplementedException();
+                        // Dispatch function to Ethernet I/O based on contents of AC0... (TBD: what are these?)
+                        // For now do nothing, since we have no Ethernet implemented
+                        //throw new NotImplementedException();
                         break;
 
                     case EmulatorF1.SWMODE:

Contralto/CPU/Tasks/Task.cs

@@ -409,8 +409,16 @@ namespace Contralto.CPU
                 return nextTask;
             }
 
-            protected abstract ushort GetBusSource(int bs);
-            protected abstract void ExecuteSpecialFunction1(MicroInstruction instruction);
+            protected virtual ushort GetBusSource(int bs)
+            {
+                // Nothing by default.
+                return 0;
+            }
+
+            protected virtual void ExecuteSpecialFunction1(MicroInstruction instruction)
+            {
+                // Nothing by default
+            }
 
             /// <summary>
             /// Used to allow Task-specific F2s that need to modify RSELECT to do so.
@@ -421,7 +429,10 @@ namespace Contralto.CPU
                 // Nothing by default.
             }
 
-            protected abstract void ExecuteSpecialFunction2(MicroInstruction instruction);
+            protected virtual void ExecuteSpecialFunction2(MicroInstruction instruction)
+            {
+                // Nothing by default.
+            }
 
             protected virtual void ExecuteSpecialFunction2Late(MicroInstruction instruction)
             {

Contralto/Contralto.csproj

@@ -48,6 +48,8 @@
     <Compile Include="CPU\ConstantMemory.cs" />
     <Compile Include="CPU\CPU.cs" />
     <Compile Include="CPU\NovaDisassembler.cs" />
+    <Compile Include="CPU\Tasks\DisplayHorizontalTask.cs" />
+    <Compile Include="CPU\Tasks\DisplayWordTask.cs" />
     <Compile Include="CPU\UCodeDisassembler.cs" />
     <Compile Include="CPU\Tasks\DiskTask.cs" />
     <Compile Include="CPU\Tasks\EmulatorTask.cs" />
@@ -61,6 +63,7 @@
     <Compile Include="Debugger.Designer.cs">
       <DependentUpon>Debugger.cs</DependentUpon>
     </Compile>
+    <Compile Include="Display\DisplayController.cs" />
     <Compile Include="IClockable.cs" />
     <Compile Include="IO\DiskController.cs" />
     <Compile Include="IO\DiabloPack.cs" />

Contralto/Display/DisplayController.cs

@@ -0,0 +1,41 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+using Contralto.Logging;
+
+namespace Contralto.Display
+{
+    /// <summary>
+    /// DisplayController implements hardware controlling the virtual electron beam
+    /// as it scans across the screen.  It implements the logic of the display's sync generator
+    /// and wakes up the DVT and DHT tasks as necessary during a display field.
+    /// </summary>
+    public class DisplayController : IClockable
+    {
+        public DisplayController(AltoSystem system)
+        {
+            _system = system;
+            Reset();
+        }
+
+        public void Reset()
+        {
+            _evenField = true;
+        }
+
+        public void Clock()
+        {
+            // TODO: Move the electron beam appropriately and wake up the display tasks
+            // as necessary.
+        }
+
+
+        bool _evenField;
+
+
+        private AltoSystem _system;
+    }
+}

Contralto/IO/DiskController.cs

@@ -368,7 +368,7 @@ namespace Contralto.IO
                 // And figure out how long this will take.
                 _seekClocks = CalculateSeekTime();
                 _elapsedSeekTime = 0.0;
-
+                
                 Log.Write(LogComponent.DiskController, "Seek to {0} from {1} commencing.  Will take {2} clocks.", _destCylinder, _cylinder, _seekClocks);
             }
         }
@@ -384,7 +384,7 @@ namespace Contralto.IO
             //
             double seekTimeMsec = 15.0 + 8.6 * Math.Sqrt(dt);
 
-            return seekTimeMsec / AltoSystem.ClockInterval;
+            return (seekTimeMsec / AltoSystem.ClockInterval) / 100;     // div 100 to make things faster for now
         }
 
         /// <summary>

Contralto/Memory/Memory.cs

@@ -34,10 +34,11 @@ namespace Contralto.Memory
                 address += 0x10000 * GetBankNumber(task, extendedMemory);
                 ushort data = _mem[address];
 
+                /*
                 if (extendedMemory)
                 {
                     Log.Write(LogComponent.Memory, "extended memory read from {0} - {1}", Conversion.ToOctal(address), Conversion.ToOctal(data));
-                }
+                } */
 
                 return data;
             }
@@ -59,10 +60,11 @@ namespace Contralto.Memory
                 address += 0x10000 * GetBankNumber(task, extendedMemory);
                 _mem[address] = data;
 
+                /*
                 if (extendedMemory)
                 {
                     Log.Write(LogComponent.Memory, "extended memory write to {0} of {1}", Conversion.ToOctal(address), Conversion.ToOctal(data));
-                }
+                } */
             }
         }