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What is difference between system control registers located in different memory area?

jinyoung noh
Prodigy 120 points
Other Parts Discussed in Thread: TM4C129XNCZAD

Hi, 

There seems many registers over multiple memory region. 

Some GPIO configurations can be done by setting registers which are located in peripheral region(0x40000000~0x5FFFFFFF) while some GPIO configurations

can be done by setting registers which are located in System region(0xF0003800~ ).

What I meant is, for example, I can see  GPIO registers (PORTK) 0x40061000 in tm4c129xnczad.h and 0xF0000809 in sysctl.h

Both of them are referring to different memory addresses. 

I don't know what difference and it confuses me.

Can anyone please explain it to me?

  • 0
    TI__Guru**** 244380 points
    Hello Jinyoung.

    The value 0xF0000809 mentioned in the sysctl.h is the parameter to be used when configuring the enable, disable, reset, ready, etc for a peripheral. As an example 0xF0000809 is for SYSCTL_PERIPH_GPIOK which can be used in SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOK) to enable clock to GPIO Port K and that will allow access to the address 0x40061000

    Regards
    Amit
  • 0 in reply to Amit Ashara
    Prodigy 120 points
    Thanks Amit,

    Let me ask one more thing. Will an access to the address 0x40061000(GPIO Port K) cause a problem when SysCtlPerpheralEnable(SYSCTL_PERIPH_GPIOK) is not used to enable before ?
    Because I could find some examples that only use SYSCTL_RCGCGPIO_R to enable to GPIO port.
    For example, SYSCTL_RCGCGPIO_R = SYSCTL_RCGCGPIO_R9 ; but SysCtlPerpheralEnable(SYSCTL_PERIPH_GPIOK) is not used in this example.

    Jinyoung
  • 0 in reply to jinyoung noh
    TI__Guru**** 244380 points
    Hello Jinyoung.

    Yes, it will cause a problem since if the peripheral is not enabled when the address space is accessed the CPU transaction will result in a Bus Fault. The SYSCTL_RCGCGPIO_R to enable does the same thing as SysCtlPeripheralEnable. The former method is called DRM which is something we will be phasing out due to its poor readability.

    Regards
    Amit