diff --git a/module01/ex00/main.c b/module01/ex00/main.c
index 247c7c8..c29a1f6 100644
--- a/module01/ex00/main.c
+++ b/module01/ex00/main.c
@@ -49,17 +49,18 @@
 #define BUTTON2	(D, SW2)
 
 // TIME
-#define PRESCALE_VALUE				1024
+#define PRESCALE_VALUE				1024		// can be 1, 8, 64, 256, 1024
+// table 16-5 : prescale sets
 #if (PRESCALE_VALUE == 1)
-	#define PRESCALE_SET			(1 << CS10)
+	#define PRESCALE_SET			(0<<CS12 | 0<<CS11 | 1<<CS10)
 #elif (PRESCALE_VALUE == 8)
-	#define PRESCALE_SET			(1 << CS11)
+	#define PRESCALE_SET			(0<<CS12 | 1<<CS11 | 0<<CS10)
 #elif (PRESCALE_VALUE == 64)
-	#define PRESCALE_SET			(1 << CS10) | (1 << CS11)
+	#define PRESCALE_SET			(0<<CS12 | 1<<CS11 | 1<<CS10)
 #elif (PRESCALE_VALUE == 256)
-	#define PRESCALE_SET			(1 << CS12)
+	#define PRESCALE_SET			(1<<CS12 | 0<<CS11 | 0<<CS10)
 #elif (PRESCALE_VALUE == 1024)
-	#define PRESCALE_SET			(1 << CS10) | (1 << CS12)
+	#define PRESCALE_SET			(1<<CS12 | 0<<CS11 | 1<<CS10)
 #endif
 #define TIME_MS(ms)					(((F_CPU / PRESCALE_VALUE) * ms) / 1000)
 
@@ -69,7 +70,7 @@ int main() {
 	MODE_OUTPUT(LED2);
 	CLEAR_ELEM(LED2);
 
-	TCCR1B |= (PRESCALE_SET);				// 16.4 : set timer with bits CS10-12, in register TCCR1B, table 16-5 : prescale values
+	TCCR1B |= (PRESCALE_SET);				// 16.4 : set timer according to prescale value, in register TCCR1B, table 16-5 : prescale sets
 
 	while(1) {
 		if (TCNT1 >= TIME_MS(500)) {		// 16.11.4 : read timer with register TCNT1 (read/write allowed), that combines two 8 bits registers
diff --git a/module01/ex01/main.c b/module01/ex01/main.c
index 0f52965..a097c97 100644
--- a/module01/ex01/main.c
+++ b/module01/ex01/main.c
@@ -49,17 +49,18 @@
 #define BUTTON2	(D, SW2)
 
 // TIME
-#define PRESCALE_VALUE				1024
+#define PRESCALE_VALUE				1024		// can be 1, 8, 64, 256, 1024
+// table 16-5 : prescale sets
 #if (PRESCALE_VALUE == 1)
-	#define PRESCALE_SET			(1 << CS10)
+	#define PRESCALE_SET			(0<<CS12 | 0<<CS11 | 1<<CS10)
 #elif (PRESCALE_VALUE == 8)
-	#define PRESCALE_SET			(1 << CS11)
+	#define PRESCALE_SET			(0<<CS12 | 1<<CS11 | 0<<CS10)
 #elif (PRESCALE_VALUE == 64)
-	#define PRESCALE_SET			(1 << CS10) | (1 << CS11)
+	#define PRESCALE_SET			(0<<CS12 | 1<<CS11 | 1<<CS10)
 #elif (PRESCALE_VALUE == 256)
-	#define PRESCALE_SET			(1 << CS12)
+	#define PRESCALE_SET			(1<<CS12 | 0<<CS11 | 0<<CS10)
 #elif (PRESCALE_VALUE == 1024)
-	#define PRESCALE_SET			(1 << CS10) | (1 << CS12)
+	#define PRESCALE_SET			(1<<CS12 | 0<<CS11 | 1<<CS10)
 #endif
 #define TIME_MS(ms)					(((F_CPU / PRESCALE_VALUE) * ms) / 1000)
 #define PERIOD						500
diff --git a/module01/ex02/main.c b/module01/ex02/main.c
index 9844ad2..dec2985 100644
--- a/module01/ex02/main.c
+++ b/module01/ex02/main.c
@@ -49,17 +49,18 @@
 #define BUTTON2	(D, SW2)
 
 // TIME
-#define PRESCALE_VALUE				1024
+#define PRESCALE_VALUE				1024		// can be 1, 8, 64, 256, 1024
+// table 16-5 : prescale sets
 #if (PRESCALE_VALUE == 1)
-	#define PRESCALE_SET			(1 << CS10)
+	#define PRESCALE_SET			(0<<CS12 | 0<<CS11 | 1<<CS10)
 #elif (PRESCALE_VALUE == 8)
-	#define PRESCALE_SET			(1 << CS11)
+	#define PRESCALE_SET			(0<<CS12 | 1<<CS11 | 0<<CS10)
 #elif (PRESCALE_VALUE == 64)
-	#define PRESCALE_SET			(1 << CS10) | (1 << CS11)
+	#define PRESCALE_SET			(0<<CS12 | 1<<CS11 | 1<<CS10)
 #elif (PRESCALE_VALUE == 256)
-	#define PRESCALE_SET			(1 << CS12)
+	#define PRESCALE_SET			(1<<CS12 | 0<<CS11 | 0<<CS10)
 #elif (PRESCALE_VALUE == 1024)
-	#define PRESCALE_SET			(1 << CS10) | (1 << CS12)
+	#define PRESCALE_SET			(1<<CS12 | 0<<CS11 | 1<<CS10)
 #endif
 #define TIME_MS(ms)					(((F_CPU / PRESCALE_VALUE) * ms) / 1000)
 #define PERIOD						1000
diff --git a/module01/ex03/main.c b/module01/ex03/main.c
index af12460..f566966 100644
--- a/module01/ex03/main.c
+++ b/module01/ex03/main.c
@@ -50,22 +50,32 @@
 #define BUTTON2	(D, SW2)
 
 // TIME
-#define PRESCALE_VALUE				1024
+#define PRESCALE_VALUE				1024		// can be 1, 8, 64, 256, 1024
+// table 16-5 : prescale sets
 #if (PRESCALE_VALUE == 1)
-	#define PRESCALE_SET			(1 << CS10)
+	#define PRESCALE_SET			(0<<CS12 | 0<<CS11 | 1<<CS10)
 #elif (PRESCALE_VALUE == 8)
-	#define PRESCALE_SET			(1 << CS11)
+	#define PRESCALE_SET			(0<<CS12 | 1<<CS11 | 0<<CS10)
 #elif (PRESCALE_VALUE == 64)
-	#define PRESCALE_SET			(1 << CS10) | (1 << CS11)
+	#define PRESCALE_SET			(0<<CS12 | 1<<CS11 | 1<<CS10)
 #elif (PRESCALE_VALUE == 256)
-	#define PRESCALE_SET			(1 << CS12)
+	#define PRESCALE_SET			(1<<CS12 | 0<<CS11 | 0<<CS10)
 #elif (PRESCALE_VALUE == 1024)
-	#define PRESCALE_SET			(1 << CS10) | (1 << CS12)
+	#define PRESCALE_SET			(1<<CS12 | 0<<CS11 | 1<<CS10)
 #endif
 #define TIME_MS(ms)					(((F_CPU / PRESCALE_VALUE) * ms) / 1000)
 #define PERIOD						1000
 #define DUTY_CYCLE					10
 #define PERCENT(percent, period)	(((float)percent / 100) * period)
+// Table 16-4 : Waveform Generation Mode Bit Description
+#define CTC_TOP_OCR1A_IN_TCCR1B			(0<<WGM13 | 1<<WGM12)
+#define CTC_TOP_OCR1A_IN_TCCR1A									(0<<WGM11 | 0<<WGM10)
+#define CTC_TOP_ICR1_IN_TCCR1B			(1<<WGM13 | 1<<WGM12)
+#define CTC_TOP_ICR1_IN_TCCR1A									(0<<WGM11 | 0<<WGM10)
+#define FAST_PWM_TOP_OCR1A_IN_TCCR1B	(1<<WGM13 | 1<<WGM12)
+#define FAST_PWM_TOP_OCR1A_IN_TCCR1A							(1<<WGM11 | 1<<WGM10)
+#define FAST_PWM_TOP_ICR1_IN_TCCR1B		(1<<WGM13 | 1<<WGM12)
+#define FAST_PWM_TOP_ICR1_IN_TCCR1A								(1<<WGM11 | 0<<WGM10)
 
 // END MACROS
 
@@ -110,9 +120,8 @@ int main() {
 
 	MODE_OUTPUT(LED2);
 
-    SET(TCCR1A, WGM11);								// Table 16-4 : set timer in Fast PWM (Pulse With Modulation) mode with TOP = ICR1 (Mode 14)
-	SET(TCCR1B, WGM12);
-    SET(TCCR1B, WGM13);
+    TCCR1A |= FAST_PWM_TOP_ICR1_IN_TCCR1A;			// Table 16-4 : set timer in Fast PWM (Pulse With Modulation) mode with TOP = ICR1 (Mode 14)
+	TCCR1B |= FAST_PWM_TOP_ICR1_IN_TCCR1B;
 
 	SET(TCCR1A, COM1A1);							// Table 16-2 : non-inverting mode, the LED will be ON for DUTY_CYCLE% of the time (CLEAR OC1A on compare match, SET OC1A at BOTTOM)