docs/machine: idle() description generalization.

docs/library/machine.rst

@@ -58,7 +58,8 @@ Power related functions
 
    Gates the clock to the CPU, useful to reduce power consumption at any time during
    short or long periods. Peripherals continue working and execution resumes as soon
-   as any interrupt is triggered (including the systick which has a period of 1ms).
+   as any interrupt is triggered (on many ports this includes system timer
+   interrupt occuring at regular intervals on the order of millisecond).
 
 .. function:: sleep()
 

docs/wipy/general.rst

@@ -174,7 +174,8 @@ Details on sleep modes
 ----------------------
 
 * ``machine.idle()``: Power consumption: ~12mA (in WLAN STA mode). Wake sources:
-  any hardware interrupt, no special configuration required.
+  any hardware interrupt (including systick with period of 1ms), no special
+  configuration required.
 * ``machine.sleep()``: 950uA (in WLAN STA mode). Wake sources are ``Pin``, ``RTC``
   and ``WLAN``
 * ``machine.deepsleep()``: ~5uA. Wake sources are ``Pin`` and ``RTC``.