diff --git a/src/mame/drivers/hawk.cpp b/src/mame/drivers/hawk.cpp
index b3f3e9a72ee..643536f15ac 100644
--- a/src/mame/drivers/hawk.cpp
+++ b/src/mame/drivers/hawk.cpp
@@ -62,10 +62,11 @@ private:
 void hawk_state::hawk_io(address_map &map)
 {
 	map.unmap_value_high();
-	//map.global_mask(0xff);
-	//map(0x18, 0x18).nopw();
-	//map(0x40, 0x4f).rw("rtc", FUNC(msm6242_device::read), FUNC(msm6242_device::write));
-	//map(0xcd, 0xcd).noprw(); // 0x00
+	map(0x0010, 0x0010).mirror(0xff00).nopw();
+	map(0x0018, 0x0018).nopw();
+	map(0x003f, 0x003f).nopw();
+	map(0x0080, 0x00bf).noprw(); // Z180 internal registers
+	map(0x00c0, 0x00cf).mirror(0xff00).rw("rtc", FUNC(msm6242_device::read), FUNC(msm6242_device::write));
 }
 
 void hawk_state::hawk_mem(address_map &map)