diff --git a/due_obd2/obd2_timer.c b/due_obd2/obd2_timer.c
index 4f5b5c6..d5d7f67 100644
--- a/due_obd2/obd2_timer.c
+++ b/due_obd2/obd2_timer.c
@@ -20,7 +20,9 @@ void obd2_timer_reset()
   */
   /* disable interrupts */
   RTT->RTT_MR &= ~RTT_MR_ALMIEN;
-  /* clear the status register */
+  /* clear the status register (reading it clears it)
+    SAM3X datasheet section 13.4: Reading the RTT_SR status register resets the RTTINC and ALMS fields.
+  */
   RTT->RTT_SR;
   /* set the alarm value to 0*/
   RTT->RTT_AR = 0;
@@ -29,4 +31,4 @@ void obd2_timer_reset()
   /* reset the RTT*/
   RTT->RTT_MR |= RTT_MR_RTTRST;
 
-}
\ No newline at end of file
+}