- Allow HGR ROM entry point

- Don't trap unexpected entrypoint when crossing between regions via RTS
- Implement TICK handler
- Improve status printing in CPU loop

simulator/apple2.py

@@ -33,6 +33,7 @@ class AppleII(machine.Machine):
             memory.MemoryRegion(
                 "ROM", 0xd000, 0xffff,
                 entrypoints={
+                    0xf3e2: machine._Event("ROM", "HGR"),
                     0xfca8: self._Wait,
                     0xfded: machine._Event("ROM", "COUT"),
                     0xfe89: machine._Event("ROM", "Select the keyboard (IN#0)")
@@ -71,9 +72,14 @@ class AppleII(machine.Machine):
             else:
                 return self.uthernet.write_data(value)
 
+        def _tick(mode, value):
+            machine.Log("Tick", self.cpu.processorCycles)
+
         # Set up interceptors for accessing various interesting parts of the
         # memory map
         self.io_map = {
+            0xc030: (
+                machine.AccessMode.RW, "TICK", _tick),
             0xc094: (
                 machine.AccessMode.RW, "WMODE", _uther_wmode),
             0xc095: (
@@ -181,16 +187,22 @@ class AppleII(machine.Machine):
                                                          address))
 
     def Run(self, pc, trace=False):
+        ctr = 0
         self.cpu.pc = pc
         old_pc = self.cpu.pc
         while True:
             self.memory_manager.MaybeInterceptExecution(self.cpu, old_pc)
             old_pc = self.cpu.pc
             if trace:
-                print(self.cpu)
-                print("  $%04X: %s" % (
+                cpu = str(self.cpu).split("\n")
+                if ctr % 20 == 0:
+                    print(cpu[0])
+                print(cpu[1], "  $%04X: %-12s  %d" % (
                     self.cpu.pc,
-                    self.disassembler.instruction_at(self.cpu.pc)[1]))
+                    self.disassembler.instruction_at(self.cpu.pc)[1],
+                    self.cpu.processorCycles
+                ))
             self.cpu.step()
             if self.cpu.pc == old_pc:
                 break
+            ctr += 1

simulator/machine.py

@@ -61,12 +61,14 @@ class SoftSwitch:
     def set(self) -> Optional[int]:
         self.state = True
         Log(self.name, "Setting soft switch")
-        return self.callback(True)
+        if self.callback:
+            return self.callback(True)
 
     def clear(self) -> Optional[int]:
         self.state = False
         Log(self.name, "Clearing soft switch")
-        return self.callback(False)
+        if self.callback:
+            return self.callback(False)
 
     def get(self) -> int:
         Log(self.name, "Reading soft switch (%s)" % (

simulator/memory.py

@@ -71,7 +71,8 @@ class MemoryManager:
 
         if self.regions[old_pc] != self.regions[pc]:
             print("Entering region %s" % self.regions[pc].name)
-            if not handlers:
+            # Don't worry if last instruction was RTS
+            if self.memory[old_pc] != 0x60 and not handlers:
                 raise UndefinedEntryPointException(self.regions[pc], old_pc, pc)
 
         for handler in handlers:
@@ -87,8 +88,8 @@ class MemoryManager:
             self.memory.subscribe_to_write(addr_range, region.write_interceptor)
 
         if not region.writable:
-            self.memory.subscribe_to_write(addr_range,
-                                           self.DenyWritesToRegion(region))
+            self.memory.subscribe_to_write(
+                addr_range, self.DenyWritesToRegion(region))
 
         for addr in addr_range:
             self.regions[addr] = region

simulator/uthernet.py

@@ -3,7 +3,7 @@ import memory
 
 
 class Uthernet(machine.Machine):
-    """Uthernet device simulator."""
+    """Uthernet/W5100 device simulator."""
 
     def __init__(self, stream:bytes):
         memory_map = [