PIC series microcontroller low power mode (SLEEP)

    Execute a "SLEEP" instruction to enter low power mode. When entering SLEEP, WDT is cleared and then restarts counting. The PD bit in the status register F3K is set to "0", the TO bit is set to "1", and the oscillation stops (referring to the oscillation circuit at the OSC1 end). All I/O ports remain in their original state. This working mode has the lowest power consumption.

    To minimize current consumption, before entering SLEEP, all I/O ports should be at high level VDD or low level VSS, and should not be in high impedance state to avoid switching current loss. You can add pull-up or pull-down resistors to the I/O ports, or set all I/O ports to output state to avoid high impedance state (floating state).

    The RTCC terminal should also be set to VDD or VSS (by pull-up or pull-down).
    MCLR must be in high level state.

2. Wake up from sleep

    SLEEP can be awakened by WDT overflow; or by adding a low level at the MCLR terminal to wake up SLEEP. The latter wake-up method is often used in the following applications: After the system's main power is off and powered by the backup power supply (battery), execute the "SLEEP" instruction to enter low-power mode, so that the battery can maintain system data for a long time. When the main power is restored, let it generate a low level at MCLR to wake up SLEEP and reset it again. In this way, an external reset circuit needs to be added to the MCLR terminal, please refer to §1.10.5.

    When the system is powered on, the PD bit of F3 is set to "1", and after executing the "SLEEP" instruction, the PD bit is set to "0". Therefore, the PD bit can be used to determine whether the system is reset by waking up from SLEEP mode or reset after power-on. The TO bit in F3 can determine whether the system in SLEEP state is awakened by WDT overflow or by a low level at the MCLR terminal given by the outside world. These distinctions are sometimes very important, especially for some system initialization.