10:16 AM

Power-down mode

The Power-down mode is entered by setting the PD bit in the PCON register. In the Power-down mode, the clock is stopped and external interrupts are active for level sensitive interrupts only. SRAM contents are retained during Power-down; the minimum VDD level is 2.0 V.

The device exits Power-down mode through either an enabled external level sensitive interrupt or a hardware reset. The start of the interrupt clears the PD bit and exits Power-down. Holding the external interrupt pin low restarts the oscillator, the signal must hold low at least 1024 clock cycles before bringing back high to complete the exit. Upon interrupt signal restored to logic VIH, the interrupt service routine program execution resumes beginning at the instruction immediately following the instruction which invoked Power-down mode. A hardware reset starts the device similar to power-on reset.

To exit properly out of Power-down, the reset or external interrupt should not be executed before the VDD line is restored to its normal operating voltage. Be sure to hold VDD voltage long enough at its normal operating level for the oscillator to restart and stabilize (normally less than 10 ms).