Hi @yanglibin ,
In fact, the external 32khz crystal not only the RTC clock, it is also used by other other modules, eg:
1. SNVSMIX. The RTC count will not so accurate.
2. CCM. May impact lower power mode entry
3. SRC. May impact reset timing
4. csu.ap_ckil_clk // Secured Low frequency clock input for the Emergency Reset Counter
The csu_alarm_out0 output from csu_reg is passed into this module and depending on counter value, is given out after a specified amount of time
5. ewm.ckil_clk
6. gpt1.ipg_clk_32k
7. gpt2.ipg_clk_32k
8. kpp.ipg_clk_32k
9. tsc_dig.lp_clk
10. usb.ipg_clk_32k
11. usdhc1.ipg_clk_32khz
12. usdhc2.ipg_clk_32khz
13. wdog1.ipg_clk_32k
14. wdog2.ipg_clk_32k
15. wdog3.int_clk
So, if you want to remove it, please make sure the above-related clock is not used in your project.
Best Regards,
Kerry
