+#define _delay_sub_us(x) __builtin_avr_delay_cycles(x)
+
+// Serial pulse period in microseconds.
+#define SELECT_SERIAL_SPEED 1
+#if SELECT_SERIAL_SPEED == 0
+ // Very High speed
+ #define SERIAL_DELAY 4 // micro sec
+ #define READ_WRITE_START_ADJUST 30 // cycles
+ #define READ_WRITE_WIDTH_ADJUST 10 // cycles
+#elif SELECT_SERIAL_SPEED == 1
+ // High speed
+ #define SERIAL_DELAY 6 // micro sec
+ #define READ_WRITE_START_ADJUST 23 // cycles
+ #define READ_WRITE_WIDTH_ADJUST 10 // cycles
+#elif SELECT_SERIAL_SPEED == 2
+ // Middle speed
+ #define SERIAL_DELAY 12 // micro sec
+ #define READ_WRITE_START_ADJUST 25 // cycles
+ #define READ_WRITE_WIDTH_ADJUST 10 // cycles
+#elif SELECT_SERIAL_SPEED == 3
+ // Low speed
+ #define SERIAL_DELAY 24 // micro sec
+ #define READ_WRITE_START_ADJUST 25 // cycles
+ #define READ_WRITE_WIDTH_ADJUST 10 // cycles
+#elif SELECT_SERIAL_SPEED == 4
+ // Very Low speed
+ #define SERIAL_DELAY 50 // micro sec
+ #define READ_WRITE_START_ADJUST 25 // cycles
+ #define READ_WRITE_WIDTH_ADJUST 10 // cycles
+#else
+#error Illegal Serial Speed
+#endif
+
+
+#define SERIAL_DELAY_HALF1 (SERIAL_DELAY/2)
+#define SERIAL_DELAY_HALF2 (SERIAL_DELAY - SERIAL_DELAY/2)
+
+#define SLAVE_INT_WIDTH 1
+#define SLAVE_INT_RESPONSE_TIME SERIAL_DELAY