diff --git a/testhal/ATSAMA5D2/SERIAL/chconf.h b/testhal/ATSAMA5D2/SERIAL/chconf.h
index b1e3841a8..33b59452e 100755
--- a/testhal/ATSAMA5D2/SERIAL/chconf.h
+++ b/testhal/ATSAMA5D2/SERIAL/chconf.h
@@ -49,7 +49,8 @@
  * @details Frequency of the system timer that drives the system ticks. This
  *          setting also defines the system tick time unit.
  */
-#define CH_CFG_ST_FREQUENCY                 1000
+#define CH_CFG_ST_FREQUENCY                 1000              /* periodic tick. */
+//#define CH_CFG_ST_FREQUENCY                 (83000000 / 32) /* tick-less. */
 
 /**
  * @brief   Time intervals data size.