diff --git a/bsl/csl/interfaces/timer.h b/bsl/csl/interfaces/timer.h
index 7e1b7cf..76d4482 100644
--- a/bsl/csl/interfaces/timer.h
+++ b/bsl/csl/interfaces/timer.h
@@ -45,7 +45,10 @@ void timerReset(timerNo_t timer);
 void timerActivateBus(timerNo_t timer); 
 void timerEnableTimer(timerNo_t timer); 
 void timerDisableTimer(timerNo_t timer);
-void timerSetClkSource(timerNo_t timer, clkSources_t clk); 
+// -> clock source is set by the clock tree and cant be individually set. This should be done
+// in the clock domain and nt here in the timerdomain. For reference one can look at the nucleo
+// stm32f042k6 clock tree diagramm in reference Manual
+//void timerSetClkSource(timerNo_t timer, clkSources_t clk); 
 void timerSetMode(timerNo_t timer, timerMode_t mode); 
 void timerSetCountDirection(timerNo_t timer, timerCountDirection_t direction); 
 void timerSetPrescaler(timerNo_t timer, uint32_t prescaler);