Added clarifying comment

embassy-stm32/src/timer/mod.rs

@@ -29,10 +29,17 @@ pub(crate) mod sealed {
             Self::regs().cr1().modify(|r| r.set_cen(false));
         }
 
+        /// Reset the counter value to 0
         fn reset(&mut self) {
             Self::regs().cnt().write(|r| r.set_cnt(0));
         }
 
+        /// Set the frequency of how many times per second the timer counts up to the max value or down to 0.
+        ///
+        /// This means that in the default edge-aligned mode,
+        /// the timer counter will wrap around at the same frequency as is being set.
+        /// In center-aligned mode (which not all timers support), the wrap-around frequency is effectively halved
+        /// because it needs to count up and down.
         fn set_frequency(&mut self, frequency: Hertz) {
             let f = frequency.0;
             let timer_f = Self::frequency().0;
@@ -515,9 +522,5 @@ foreach_interrupt! {
                 crate::pac::$inst
             }
         }
-
-
-
-
     };
 }