[#314] Z80 frequency updates, ZXspectr contention fixes

plugins/cpu/z80-cpu/src/main/java/net/emustudio/plugins/cpu/zilogZ80/ContextZ80Impl.java

@@ -38,7 +38,7 @@ public final class ContextZ80Impl implements ContextZ80 {
     private final TimedEventsProcessor tep = new TimedEventsProcessor();
 
     private volatile EmulatorEngine engine;
-    private volatile int clockFrequency = DEFAULT_FREQUENCY_KHZ;
+    private volatile int clockFrequencyKHz = DEFAULT_FREQUENCY_KHZ;
 
     public void setEngine(EmulatorEngine engine) {
         this.engine = engine;
@@ -98,15 +98,15 @@ public void signalInterrupt(byte[] data) {
 
     @Override
     public int getCPUFrequency() {
-        return clockFrequency;
+        return clockFrequencyKHz;
     }
 
     @Override
     public void setCPUFrequency(int frequency) {
         if (frequency <= 0) {
             throw new IllegalArgumentException("Invalid CPU frequency (expected > 0): " + frequency);
         }
-        clockFrequency = frequency;
+        clockFrequencyKHz = frequency;
     }
 
     @Override

plugins/cpu/z80-cpu/src/main/java/net/emustudio/plugins/cpu/zilogZ80/EmulatorEngine.java

@@ -36,6 +36,7 @@
 import java.util.Queue;
 import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
@@ -203,8 +204,11 @@ public CPU.RunState run(CPU cpu) {
         // in 1 millisecond time slice = 1 / 0.00025 = 4000 t-states are executed uncontrollably
 
         long timeSliceNanos = SleepUtils.SLEEP_PRECISION;
-        int timeSliceMillis = (int) Math.ceil(timeSliceNanos / 1000000.0);
-        int cyclesPerTimeSlice = timeSliceMillis * context.getCPUFrequency();
+        double timeSliceMicros = timeSliceNanos / 1_000.0;
+        int cyclesPerTimeSlice = (int) (timeSliceMicros * context.getCPUFrequency() / 1000.0); // frequency in kHZ -> MHz
+
+        //System.out.println("Time slice millis: " + timeSliceMillis);
+        //System.out.println("Cycles per time slice: " + cyclesPerTimeSlice);
 
         currentRunState = CPU.RunState.STATE_RUNNING;
         while (!Thread.currentThread().isInterrupted() && (currentRunState == CPU.RunState.STATE_RUNNING)) {
@@ -248,7 +252,13 @@ private int dispatch() throws Throwable {
             lastQ = Q;
             Q = 0;
             if (pendingNonMaskableInterrupt.getAndSet(false)) {
-                writeWord((SP - 2) & 0xFFFF, PC);
+                if (memory.read(PC) == 0x76) {
+                    // jump over HALT
+                    writeWord((SP - 2) & 0xFFFF, (PC + 1) & 0xFFFF);
+                } else {
+                    writeWord((SP - 2) & 0xFFFF, PC);
+                }
+
                 SP = (SP - 2) & 0xffff;
                 PC = 0x66;
                 return 12;

plugins/device/cassette-player/src/main/java/net/emustudio/plugins/device/cassette_player/PlaybackListenerImpl.java

@@ -28,9 +28,18 @@
 
 // Pulse length:
 // https://worldofspectrum.org/faq/reference/48kreference.htm
+// https://softspectrum48.weebly.com/notes/tape-loading-routines
 
 //Machine	Pilot pulse	Length	Sync1	Sync2	Bit 0	Bit 1
-//ZX Spectrum	2168	(1)	667	735	855	1710
+//ZX Spectrum	2168	(1)  	667 	735 	855 	1710
+
+// Tape data is encoded as two 855 T-state pulses for binary zero, and two 1,710 T-state pulses for binary one.
+
+// To distinguish header blocks from data blocks, a sequence of leader pulses precedes each type of block.
+// The leader pulse is 2,168 T-states long and is repeated 8,063 times for header blocks and 3,223 times for data blocks.
+//
+// After the leader pulses, two sync pulses (667 T-states plus 735 T-states long) follow to signal the beginning of the
+// actual data.
 public class PlaybackListenerImpl implements Loader.PlaybackListener {
     private final DeviceContext<Byte> bus;
     private final AtomicReference<CassettePlayerGui> gui = new AtomicReference<>();
@@ -81,4 +90,8 @@ public void onStateChange(CassetteController.CassetteState state) {
     private void log(String message) {
         Optional.ofNullable(gui.get()).ifPresent(g -> g.setMetadata(message));
     }
+
+    private void pulse(boolean active, int howLong) {
+
+    }
 }

plugins/device/zxspectrum-bus/src/main/java/net/emustudio/plugins/device/zxspectrum/bus/ZxSpectrumBusImpl.java

@@ -64,36 +64,47 @@
  * tstates and continues for all 192 lines of screen data. After this, there is no delay until the end of the
  * frame as the bottom border and vertical refresh happen, and no delay until 14335 tstates after the start of
  * the next frame as the top border is drawn.
+ * <p>
+ * Contended I/O
+ * High byte   |         |
+ * in 40 - 7F? | Low bit | Contention pattern
+ * ------------+---------+-------------------
+ * No          |  Reset  | N:1, C:3
+ * No          |   Set   | N:4
+ * Yes         |  Reset  | C:1, C:3
+ * Yes         |   Set   | C:1, C:1, C:1, C:1
  */
 @NotThreadSafe
 public class ZxSpectrumBusImpl extends AbstractMemoryContext<Byte> implements ZxSpectrumBus {
+    private final static int SCREEN_LINES = 192;
+    private final static int CONTENTION_TSTATE_START = 14335;
+    private static final int CPU_INTERRUPT_TSTATES = 69888;
+
     private ContextZ80 cpu;
     private MemoryContext<Byte> memory;
     private volatile byte busData; // data on the bus
-    private TimedEventsProcessor ted;
-    private boolean lastMemoryContended = false;
+    private TimedEventsProcessor tep;
+    private boolean isContended = false;
 
     private final Map<Integer, Context8080.CpuPortDevice> deferredAttachments = new HashMap<>();
 
-
     public void initialize(ContextZ80 cpu, MemoryContext<Byte> memory) {
         this.cpu = Objects.requireNonNull(cpu);
         this.memory = Objects.requireNonNull(memory);
-        this.ted = cpu.getTimedEventsProcessor().orElseThrow(() -> new RuntimeException("CPU must provide TimedEventProcessor"));
+        this.tep = cpu.getTimedEventsProcessor().orElseThrow(() -> new RuntimeException("CPU must provide TimedEventProcessor"));
 
         for (Map.Entry<Integer, Context8080.CpuPortDevice> attachment : deferredAttachments.entrySet()) {
-            // TODO: contended device proxy if needed
-            if (!cpu.attachDevice(attachment.getKey(), attachment.getValue())) {
+            if (!cpu.attachDevice(attachment.getKey(), new ContendedDeviceProxy(attachment.getValue()))) {
                 throw new RuntimeException("Could not attach device " + attachment.getValue().getName() + " to CPU");
             }
         }
 
         //  17 x from 14335 to 14463, then 96 tstates pause to reach "end of line", then repeat.
         // the t-state 14335 is the first screen line to be read.
-        int cycles = 14335;
-        for (int line = 0; line < 192; line++) {
+        int cycles = CONTENTION_TSTATE_START + CPU_INTERRUPT_TSTATES;
+        for (int line = 0; line < SCREEN_LINES; line++) {
             scheduleMemoryContention(cycles);
-            cycles = cycles + 16 * 8 + 96;
+            cycles = cycles + 17 * 8 + 96 - 1;
         }
     }
 
@@ -104,7 +115,7 @@ public void attachDevice(int port, Context8080.CpuPortDevice device) {
             deferredAttachments.put(port, device);
         } else {
             // TODO: contended device proxy if needed
-            if (!cpu.attachDevice(port, device)) {
+            if (!cpu.attachDevice(port, new ContendedDeviceProxy(device))) {
                 throw new RuntimeException("Could not attach device " + device.getName() + " to CPU");
             }
         }
@@ -195,18 +206,48 @@ public MemoryContextAnnotations annotations() {
     }
 
     private void setContended(int location) {
-        this.lastMemoryContended = location >= 0x4000 && location <= 0x7FFF;
+        this.isContended = location >= 0x4000 && location <= 0x7FFF;
     }
 
     private void scheduleMemoryContention(int startCycles) {
+        //  17 x from 14335 to 14463, then 96 tstates pause to reach "end of line", then repeat.
+        Runnable slowDownByOneCycle = () -> {
+            if (isContended) {
+                cpu.addCycles(1);
+            }
+        };
+
         for (int i = 0; i < 17; i++) {
             for (int j = 0; j < 6; j++) {
-                ted.schedule(startCycles + i * 8 + j, () -> {
-                    if (lastMemoryContended) {
-                        cpu.addCycles(1);
-                    }
-                });
+                tep.schedule(startCycles + i * 8 + j, slowDownByOneCycle);
             }
         }
     }
+
+    private class ContendedDeviceProxy implements Context8080.CpuPortDevice {
+        private final Context8080.CpuPortDevice device;
+
+        private ContendedDeviceProxy(Context8080.CpuPortDevice device) {
+            this.device = Objects.requireNonNull(device);
+        }
+
+        @Override
+        public byte read(int portAddress) {
+            setContended(portAddress);
+            // TODO: portAddress & 1 == 0  ==> contended for 3 cycles only
+            return device.read(portAddress);
+        }
+
+        @Override
+        public void write(int portAddress, byte data) {
+            setContended(portAddress);
+            // TODO: portAddress & 1 == 0  ==> contended for 3 cycles only
+            device.write(portAddress, data);
+        }
+
+        @Override
+        public String getName() {
+            return device.getName();
+        }
+    }
 }

plugins/device/zxspectrum-ula/src/main/java/net/emustudio/plugins/device/zxspectrum/ula/gui/DisplayCanvas.java

@@ -81,13 +81,13 @@ public class DisplayCanvas extends Canvas implements AutoCloseable {
     private volatile Dimension size = new Dimension(0, 0);
 
     private final ULA ula;
-    private final TimedEventsProcessor ted;
+    private final TimedEventsProcessor tep;
     private final PaintCycle paintCycle = new PaintCycle();
     private int interrupts = 0;
 
     public DisplayCanvas(ULA ula) {
         this.ula = Objects.requireNonNull(ula);
-        this.ted = ula.getTimedEventsProcessor();
+        this.tep = ula.getTimedEventsProcessor();
         this.screenImage.setAccelerationPriority(1.0f);
         this.screenImageData = ((DataBufferInt) this.screenImage.getRaster().getDataBuffer()).getData();
     }
@@ -96,11 +96,11 @@ public void start() {
         if (painting.compareAndSet(false, true)) {
             createBufferStrategy(2);
 
-            ted.schedule(REPAINT_CPU_TSTATES, this::triggerCpuInterrupt);
-            ted.schedule(REPAINT_CPU_TSTATES, ula::onNextFrame);
+            tep.schedule(REPAINT_CPU_TSTATES, this::triggerCpuInterrupt);
+            tep.schedule(REPAINT_CPU_TSTATES, ula::onNextFrame);
             for (int i = 0; i < SCREEN_IMAGE_HEIGHT; i++) {
                 int finalI = i;
-                ted.schedule(i * LINE_CPU_TSTATES + 1, () -> drawNextLine(finalI));
+                tep.schedule(i * LINE_CPU_TSTATES + 1, () -> drawNextLine(finalI));
             }
         }
     }
@@ -187,10 +187,10 @@ public void setBounds(Rectangle r) {
 
     @Override
     public void close() {
-        ted.remove(REPAINT_CPU_TSTATES, paintCycle);
+        tep.remove(REPAINT_CPU_TSTATES, paintCycle);
         for (int i = 0; i < SCREEN_IMAGE_HEIGHT; i++) {
             int finalI = i;
-            ted.remove(i * LINE_CPU_TSTATES, () -> drawNextLine(finalI));
+            tep.remove(i * LINE_CPU_TSTATES, () -> drawNextLine(finalI));
         }
         painting.set(false);
     }