XC886/888CLM
Power Saving Modes
User’s Manual
8-4
V1.3, 2010-02
Power Saving Modes, V 1.0
Exiting Power-down Mode
If power-down mode is exited via a hardware reset, the device is put into the hardware
reset state.
When the wake-up source and wake-up type have been selected prior to entering
power-down mode, the power-down mode can be exited via EXINT0 pin/RXD pin.
Bits MODPISEL.URRIS and MODPISEL.URRISH are used to select one of the three
RXD inputs and bit MODPISEL.EXINT0IS is used to select one of the two EXINT0
inputs.
If bit WKSEL was set to 1 before entering power-down mode, the system will execute a
reset sequence similar to the power-on reset sequence. Therefore, all port pins are put
into their reset state and will remain in this state until they are affected by program
execution.
If bit WKSEL was cleared to 0 before entering power-down mode, a fast wake-up
sequence is used. The port pins continue to hold their state which was valid during
power-down mode until they are affected by program execution.
The wake-up from power-down without reset undergoes the following procedure:
1. In power-down mode, EXINT0 pin/RXD pin must be held at high level.
2. Power-down mode is exited when EXINT0 pin/RXD pin goes low for at least 100 ns.
3. The main voltage regulator is switched on and takes approximately 150
µ
s to
become stable.
4. The on-chip oscillator and the PLL are started. Typically, the on-chip oscillator takes
approximately 500 ns to stabilize. The PLL will be locked within 200
µ
s after the
on-chip oscillator clock is detected for stable nominal frequency. If the external
oscillator is used as the PLL input clock source, only the time to lock the PLL needs
to be taken into consideration.
5. Subsequently, the FLASH will enter ready-to-read mode. This does not require the
typical 160
µ
s as is the case for the normal reset. The timing for this part can be
ignored.
6. The CPU operation is resumed. The core will return to execute the next instruction
after the instruction which sets the PD bit.
Note: No interrupt will be generated by the EXINT0 wake-up source even if EXINT0 is
enabled before entering power-down mode. An interrupt will be generated only if
EXINT0 fulfils the interrupt generation conditions after CPU resumes operation.
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