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J7200XSOMXEVM: How to modify MMR

zhaofei li
Prodigy 60 points
Part Number: J7200XSOMXEVM
Other Parts Discussed in Thread: DRA821

I am using J7200XSOMXEVM to evaluate the uart of dra821. I tried to modify the uart baud rate to 12M based on the SDK demo “csl_uart_test_app”. According to the Technical Reference Manual of DRA821, I need to modify CTRLMMR_USART0_CLK_CTRL, set CLK_DIV to 0h-Divide by 1, and the input clock has been set to 192MHz, so I can set the baud rate to 12M. In the Technical Reference Manual, CTRL_MMR0 has 2 offsets: Proxy0 Offset and Proxy1 Offset, as well as 2 physical addresses. I tried to use the CTRL_MM R0_CFG0 Proxy0 Physical Address in the document to modify it, but it didn't seem to work. I have set up the MMR unlock before this. So what should I do to modify CTRLMMR_USART0_CLK_CTRL? What should be the correct step?

  • 0
    TI__Genius 10180 points

    Zhaofei,

    To set the divider value bit 16 of the same register has to be cleared and then set to 1.  Have you done that?  Also which register did you unlock?  CTRLMMR_LOCK2 is the corresponding register to update.

    Thanks & Regards,

    Shiou Mei

  • 0 in reply to Shiou Mei Huang
    Prodigy 60 points

    I unlocked from lock0 to lock7 to make sure that it won't affect my modification of the register.

    Then I tried to write 0 to CTRLMMR_USART0_CLK_CTRL, and the read back value proved that I had changed CTRLMMR_USART0_CLK_CTRL to 0, but the clock sent to uart was still divided to 48MHz.

    So, I am not sure I really modified the register.

    I suspect that my steps are wrong. These caused the register not to be actually modified, or the modification did not work.

  • 0 in reply to Shiou Mei Huang
    Prodigy 60 points

    Now I can manually modify the MMR through CCS. I also need to modify the MMR through code. According to the user manual, each MMR register has 2 addresses: CTRL_MMR0_CFG0 Proxy0 Physical Address and CTRL_MM R0_CFG0 Proxy1 Physical Address. How to determine which address should be used?

  • +1
    TI__Genius 10180 points

    Zhaofei,

    Proxy0 is designed for non-safety software (i.e. Linux), whereas proxy1 is designed for safety software (i.e. RTOS).

    Best Regards,

    Shiou Mei