[#65][Python] Support enitering and exiting the halted mode manually.

And give an example.

Author: kosarev

examples/exit_halted_state.oy

@@ -0,0 +1,36 @@
+#!/usr/bin/env python3
+
+import z80
+
+
+def main():
+    INC_A = 0x3c
+    HALT = 0x76
+
+    code = bytes([INC_A, HALT, INC_A])
+
+    m = z80.Z80Machine()
+    m.set_memory_block(0x0000, code)
+
+    def step():
+        m.ticks_to_stop = 1
+        m.run()
+
+        print(f'pc={m.pc:04x} a={m.a:02x} halted={m.halted}')
+
+    # Execute the first 'inc a'.
+    step()
+
+    # Execute the halt.
+    # From now on, stepping will not progress until we exit the halted mode.
+    step()
+    step()
+    step()
+
+    # Exit the halted mode and execute the second 'inc a'.
+    m.halted = False
+    step()
+
+
+if __name__ == "__main__":
+    main()

z80/_machine.py

@@ -298,7 +298,11 @@ def int_disabled(self):
 
     @property
     def halted(self):
-        return self.__halted[0]
+        return bool(self.__halted[0])
+
+    @halted.setter
+    def halted(self, value):
+        self.__halted[0] = int(value)
 
     @property
     def index_rp_kind(self):