diff --git a/boop/audio/soundirq.c b/boop/audio/soundirq.c
index 2b06570..81635e7 100644
--- a/boop/audio/soundirq.c
+++ b/boop/audio/soundirq.c
@@ -35,7 +35,6 @@ extern volatile char last_sample;
 */
 
 unsigned int tval;
-unsigned char bl_val, cmp_val;	// backlight PWM
 unsigned int slen;
 unsigned char *sdata;
 unsigned char sact;
@@ -211,16 +210,4 @@ void __attribute__ ((section(".text.fastcode"))) soundIRQ (void)
 		}
 	}
 	
-/*	// backlight pwm
-	cmp_val += bl_val;
-	if (cmp_val >= 63) 
-	{
-		FIODIR0 |= (1<<4);		// sck0/P0.4
-		cmp_val -= 63;
-	} 
-	else 
-	{
-		FIODIR0 &= ~(1<<4);		// sck0/P0.4
-	}
-*/
 }
diff --git a/boop/boop_rom.bin b/boop/boop_rom.bin
index 5a46ad7..dc098e9 100644
Binary files a/boop/boop_rom.bin and b/boop/boop_rom.bin differ
diff --git a/boop/timer/timerfuncs.c b/boop/timer/timerfuncs.c
index f7749c1..7467050 100644
--- a/boop/timer/timerfuncs.c
+++ b/boop/timer/timerfuncs.c
@@ -42,7 +42,7 @@ void startTimerIRQ(void)
 	T0TCR = 0x02;	// reset timer
 	T0TC = 1870;
 	T0PR = 0x0e; 	// 15.000.000 Hz / 15 = 1.000.000 Hz --> PR = 15 - 1 = 0x0e
-	T0MR0 = 5000;	//  1.000.000 Hz / 5000 =  200 Hz = 5 msec intervall time
+	T0MR0 = 250;	//  1.000.000 Hz / 250 =  4000 Hz = 0,25msec intervall time
 	T0MCR = 0x03;	// reset and issue IRQ on TC == MR0
 	T0TCR = 0x01;	// enable timer
 	
diff --git a/boop/timer/timerirq.c b/boop/timer/timerirq.c
index a19cfae..873274f 100644
--- a/boop/timer/timerirq.c
+++ b/boop/timer/timerirq.c
@@ -21,14 +21,37 @@
 #include "timerfuncs.h"
 #include "lcd.h"
 
+#define TIMER_PRESCALER		20
+
 struct CB callbacks[MAX_CB];
 unsigned long* timeouts[MAX_TO];
+unsigned char timerPrescaler = TIMER_PRESCALER;
+unsigned char bl_val, cmp_val;	// backlight PWM
 
-
-// wird alle 5 ms aufgerufen (s. startTimerIRQ() in timerfuncs)
+// wird alle 0.25 ms aufgerufen (s. startTimerIRQ() in timerfuncs)
 // bearbeitet eingetragene "timer"
 void __attribute__ ((section(".text.fastcode"))) timerIRQ(void)
 {
+	// backlight pwm
+	cmp_val += bl_val;
+	if (cmp_val >= 63)
+	{
+		FIODIR0 |= (1<<4);		// sck0/P0.4
+		cmp_val -= 63;
+	}
+	else
+	{
+		FIODIR0 &= ~(1<<4);		// sck0/P0.4
+	}
+
+
+	if(--timerPrescaler) {
+		T0IR = 1;
+		return;
+	}
+	timerPrescaler = TIMER_PRESCALER;
+
+	//5 msec intervall time
 	unsigned int cnt;
 	struct CB *cur_cb;