SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
The clock reference for the RTC is an internal 32-kHz clock signal (RTC_AUX_CLK from PRCM) or an external clock source of the 32.768 Hz frequency on the RTC_32K_CLK pin.
The RTC_DISABLE bit in the control register (RTC_CTRL_REG) can be set to save power; however, the RTC_DISABLE bit is not to be cleared once it has been set. If the application requires the RTC module to stop and continue, the STOP_RTC bit in RTC_CTRL_REG is used instead.
The selection between external and internal clock is done through the RTC_OSC_REG register. Setting the RTC_OSC_REG[3] K32CLK_SEL = 1 selects the 32-kHz external/oscillator clock (RTC_32K_CLK), setting it to 0 selects the PRCM clock (RTC_AUX_CLK). RTC_OSC_REG[2] RES_SELECT enables the internal feedback resistor. By modifying the RTC_OSC_REG[4] OSC32K_GZ bit, software enables or disables the 32-kHz oscillator.
If the RTC module or RTC oscillator is not used, the rtc_osc_xi_clkin32 device pin should be held low and rtc_osc_xo should be left unconnected. For more information about rtc pin connection if RTC is not used in the design, see the device-specific data manual.