ST ST10F276E - Figure 211. RPD Pin: External Circuit to Exit Power down

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UM0404 Power reduction modes
Exiting power down mode
When Interruptible Power Down mode is entered, the CPU and peripheral clocks are frozen,
and the oscillator and PLL are stopped (when RTC is disabled, so there is no need for a
clock reference). Interruptible Power Down mode can be exited by either asserting RSTIN
or one of the enabled EXxIN pin (Fast External Interrupt). In case the Real Time Clock
module needs to be running during Power Down, either the main or the low-power oscillator
is not stopped. The PLL, on the contrary is anyway switched off.
If Power Down mode is exited by a hardware RESET, RSTIN
pin must be held low until the
oscillator (if not already running for Real Time Clock operation) and PLL have restarted and
stabilized.
EXxIN inputs are normally sampled interrupt inputs. However, the Power Down mode
circuitry uses them as level-sensitive inputs. An EXxIN (x = 7...0) Interrupt Enable bit (bit
CCxIE in respective CCxIC register) needs not to be set to bring the device out of Power
Down mode.
In order to guarantee a proper stabilization time before restart the operation when exiting
from Power Down (especially if the main oscillator was stopped: typically when Real Time
Clock module is not used, or when the low-power on-chip oscillator circuit is used to provide
the reference signal to the Real Time Clock module), an external RC circuit must be
connected to RPD pin (Return from Power Down), as shown in the following Figure 211.
Figure 211. RPD pin: external circuit to exit power down
To exit Power Down mode with external interrupt, an EXxIN pin has to be asserted for at
least 40ns (x = 7...0). This signal enables the internal main oscillator (if not already running)
and PLL circuitry, and also turns on the internal weak pull-down on RPD pin (see following
Bit Function
EXIxES
(x
= 7...0)
External Interrupt x Edge Selection Field (x
= 7...0)
0 0: Fast external interrupts disabled: standard mode
EXxIN pin not taken in account for entering/exiting Power Down mode.
0 1: Interrupt on positive edge (rising)
Enter Power Down mode if EXiIN = ‘0’, exit if EXxIN = ‘1’ (ref as ‘high’ active level)
1 0: Interrupt on negative edge (falling)
Enter Power Down mode if EXiIN = ‘1’, exit if EXxIN = ‘0’ (ref as ‘low’ active level)
1 1: Interrupt on any edge (rising or falling)
Always enter Power Down mode, exit if EXxIN level changed.
RPD
220 k-1M Ohm (Typ)
1μF (Typ)
ST10F276
+
V
DD
C0
R0