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tests/test_p9_bus.py

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+import unittest
+
+from h8536.emulator import MemoryMap, P9DDR, P9DR
+from h8536.emulator.peripherals import P9Bus
+
+
+class P9BusTest(unittest.TestCase):
+    def test_bit7_input_uses_queued_then_default_low_response(self):
+        memory = MemoryMap(b"\x00" * 4)
+        memory.write8(P9DDR, 0x13)
+        memory.write8(P9DR, 0x80)
+        memory.p9_bus.queue_input_bits([1])
+
+        self.assertEqual(memory.read8(P9DDR), 0x13)
+        self.assertEqual(memory.read8(P9DR) & 0x80, 0x80)
+        self.assertEqual(memory.read8(P9DR) & 0x80, 0x00)
+        self.assertEqual(memory.registers[P9DR - 0xFE80], 0x80)
+
+    def test_bit7_output_reads_latch(self):
+        memory = MemoryMap(b"\x00" * 4)
+        memory.write8(P9DDR, 0x93)
+        memory.write8(P9DR, 0x80)
+
+        self.assertEqual(memory.read8(P9DDR), 0x93)
+        self.assertEqual(memory.read8(P9DR) & 0x80, 0x80)
+        self.assertEqual(memory.registers[P9DR - 0xFE80], 0x80)
+
+    def test_strobe_rising_edges_capture_output_bits_and_byte_candidates(self):
+        bus = P9Bus()
+        bus.write_ddr(0x93)
+        for bit in (1, 0, 1, 0, 0, 1, 0, 1):
+            bus.write_dr(0x80 if bit else 0x00)
+            bus.write_dr((0x80 if bit else 0x00) | 0x02)
+            bus.write_dr(0x80 if bit else 0x00)
+
+        self.assertEqual(bus.transmitted_bits, [1, 0, 1, 0, 0, 1, 0, 1])
+        self.assertEqual(bus.byte_candidates, [0xA5])
+        self.assertEqual([event.edge for event in bus.strobe_edges[:2]], ["rising", "falling"])
+
+
+if __name__ == "__main__":
+    unittest.main()