In STANDBY mode, the CPU, SRAM, and PD1 peripherals
are disabled and in retention. PD0 peripherals, are available with a maximum
ULPCLK frequency of 32kHz. High-speed oscillators such as SYSPLL, HFXT, HFCLK_IN and SYSOSC
are disabled. Wakeup sources includes
digital peripherals like I2C, UART start detection, PD0 timers
elapsing, RTC wakeup, GPIO toggle.
There are 2 policy options for STANDBY mode: STANDBY0 and STANDBY1.
- STANDBY0: All PD0 peripherals receive the
ULPCLK and LFCLK, while the
RTC receives the RTCCLK.
can synchronously wakeup the device. Comparator wakeup is not
supported to avoid high power consumption.
- STANDBY1: Only a few general purpose timers receive ULPCLK or LFCLK,
see the device-specific data sheet to determine them. If the device contains an
RTC module, it continues to receive RTCCLK. A general timer interrupt, RTC
interrupt, or GPIO interrupt triggers an asynchronous fast clock request to wake
the system. Other PD0 peripherals (such as UART, I2C, GPIO) can also wake the
system upon an external event through an asynchronous fast clock request, but
they are not actively clocked in STANDBY1.