EMualtor adjustments

tests/test_emulator_addressing.py

@@ -0,0 +1,63 @@
+import unittest
+
+from h8536.emulator import H8536Emulator
+
+
+def rom_with_reset(*, reset: int = 0x1000, size: int = 0x1100) -> bytearray:
+    rom = bytearray([0xFF] * size)
+    rom[0:2] = reset.to_bytes(2, "big")
+    return rom
+
+
+class EmulatorAddressingTest(unittest.TestCase):
+    def test_txi_indexed_byte_load_uses_signed_word_displacement_and_full_index_register(self):
+        rom = rom_with_reset()
+        rom[0x1000:0x1004] = b"\xF0\xF8\x58\x80"  # MOV:G.B @(-H'07A8,R0), R0
+
+        emulator = H8536Emulator(bytes(rom))
+        emulator.cpu.regs[0] = 5
+        emulator.memory.write8(0xF85D, 0xA6)
+        emulator.step()
+
+        self.assertEqual(emulator.cpu.regs[0], 0x00A6)
+        self.assertEqual(emulator.cpu.pc, 0x1004)
+
+    def test_txi_indexed_byte_load_preserves_destination_high_byte(self):
+        rom = rom_with_reset()
+        rom[0x1000:0x1004] = b"\xF0\xF8\x58\x80"  # MOV:G.B @(-H'07A8,R0), R0
+
+        emulator = H8536Emulator(bytes(rom))
+        emulator.cpu.regs[0] = 0x0105
+        emulator.memory.write8(0xF95D, 0x4B)
+        emulator.step()
+
+        self.assertEqual(emulator.cpu.regs[0], 0x014B)
+
+    def test_extu_byte_clears_high_byte_before_txi_indexed_load(self):
+        rom = rom_with_reset()
+        rom[0x1000:0x1002] = b"\xA0\x12"  # EXTU.B R0
+        rom[0x1002:0x1006] = b"\xF0\xF8\x58\x80"  # MOV:G.B @(-H'07A8,R0), R0
+
+        emulator = H8536Emulator(bytes(rom))
+        emulator.cpu.regs[0] = 0x0105
+        emulator.memory.write8(0xF85D, 0xC7)
+        emulator.memory.write8(0xF95D, 0x99)
+        emulator.run(max_steps=2)
+
+        self.assertEqual(emulator.cpu.regs[0], 0x00C7)
+        self.assertEqual(emulator.cpu.pc, 0x1006)
+
+    def test_signed_byte_displacement_addresses_below_base(self):
+        rom = rom_with_reset()
+        rom[0x1000:0x1003] = b"\xE1\xFE\x81"  # MOV:G.B @(H'-02,R1), R1
+
+        emulator = H8536Emulator(bytes(rom))
+        emulator.cpu.regs[1] = 0xFE90
+        emulator.memory.write8(0xFE8E, 0x37)
+        emulator.step()
+
+        self.assertEqual(emulator.cpu.regs[1], 0xFE37)
+
+
+if __name__ == "__main__":
+    unittest.main()