ST10R272L - POWER REDUCTION MODES
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When the RPD/Vpp voltage drops below the threshold voltage (2.0V for the 3.3V device and
2.5V for the 5V device), the Schmitt trigger clears Q2 flip-flop (see
Figure 119). This enables
the CPU and Peripheral clocks. The device resumes code execution.
If the Interrupt was enabled (bit CCxIE=’1’ in the respective CCxIC register) before entering
Power Down mode, the device executes the interrupt service routine, and then resumes
execution after the PWRDN instruction (see note below). If the interrupt was disabled, the
device executes the instruction following PWRDN instruction, and the Interrupt Request Flag
(bit CCxIR in the respective CCxIC register) remains set until it is cleared by software.
Note
Due to internal pipeline, the instruction that follows the PWRDN instruction is
executed before the CPU performs a call of the interrupt service routine.
Figure 118 Powerdown exit sequence when using an external interrupt
(PLL multiply factor of 2)
CPU clk
internal
External
V
PP
/RPD
ExitPwrd
XTAL1
signal
Interrupt
(internal)
see note
delay for oscillator/pll
stabilization
Powerdown
Internal Pullup
Action
External R
Action
Note: 2.0V for the 3.3V device and
2.5V for the 5V device