+/*
+ * control register bits
+ */
+/* read MPU401C() */
+#define MPU401_RX_EMPTY 0x80
+#define MPU401_TX_FULL 0x40
+
+/* write MPU401C() */
+#define MPU401_RESET 0xff
+#define MPU401_ENTER_UART 0x3f
+
+/* read MPU401D() */
+#define MPU401_ACK 0xfe
+
+