Hello Friends,
I am using custom mx28 board with 5V only supply. It has powersupply for RTC as below. Board has 32.768 KHz and 24 MHz crystal. I would like to run the RTC on power down via 32 KHz crystal instead of 24 MHz crystal.
At the U-Boot prompt, when I tried setting the HW_RTC_PERSISTENT0 register value to 0x121 (Keeping Clock source as 32 KHz and powering up xtal 32 KHz via setting bits CLOCKSOURCE and XTAL32KHZ_PWRUP) as below:
MX28EVK U-Boot > mm 0x80056060
80056060: 00020100 ? 121
After that, I can see the Clock on 32 KHz and 24 MHz which is good. Now when I power down the board, I still see both Clocks running instead of only 32 KHz for RTC. Can anyone share some comments or concerns?
Thank you,
Ankur.
Hi Ankur
how did you power down chip , was 5V
completely removed ? Also had HW_RTC_PERSISTENT0 register
retained previous value, which was written to it before power down ?
Actually one can use BitBurner.exe to program the OCOTP bits manually.
Hello Chipexpert,
Thank you for your response.
Yes, we are power down the Chip with 5V power supply off.
And I have checked with the register value HW_RTC_PERSISTENT0 which remain persistent after power cycle as below:
Steps:
1) Power on the Board with 5V power supply
2) At U-boot prompt updated the value of HW_RTC_PERSISTENT0 register to 0x121
3) Verify and the value of HW_RTC_PERSISTENT0 is 0x121
4) Power off the 5V power supply from the board.
5) Wait for 5 Min
6) Power on the Board with 5V power supply
7) Verify the value of register HW_RTC_PERSISTENT0 and found to be 0x121
It means the value remains persistent in HW_RTC_PERSISTENT0.
Moreover, I have check with OCOTP section for enabling XTAL 32 KHz clock for RTC. But Is it mandatory to enable bit
RTC_XTAL_32768_PRESENT under HW_OCOTP_CUSTCAP regsister so as only 32 KHz clocks run on power down and disables 24 MHz clock?
Regards,
Ankur
Ahh!! It was hardware issue. PSWITCH was pulled high. Now RTC works smooth..
Appreciate your time and response.
Regards,
Ankur.
Thank you all..