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Original question:

TM4C129XNCZAD: How to select between the Advanced High-Performance Bus (AHB), and Advanced Peripheral Bus (APB)

TM4C1231H6PM: Debugging GPIO ports does not work if they run on AHB bus

Johannes Lang
Prodigy 40 points
Part Number: TM4C1231H6PM

hi fellows,

when I have the AHB Bus enabled (GPIOHBCTL) I cannot see the register content in the Debug Mode and get the following error message.

CORTEX_M4_0: Trouble Reading Memory Block at 0x40025518 on Page 0 of Length 0x4: Debug Port error occurred.

Is this an expected behaviour?

Greets

Side notes: I do not use Tivaware but I strictly follow the initalization suggestion from page 673 10.3 Initalization and Configuration of the data sheet.

  • 0
    TI__Guru*** 135355 points

    Hello Johannes,

    That would mean the peripheral has not been correctly configured.

    For TivaWare, to enable AHB, we use the following code:

    SysCtlGPIOAHBEnable(SYSCTL_PERIPH_GPIOF);

    I imagine you are missing that SysCtl setting. When I removed that line, I was able to recreate your error.

    By the way, it is a rare case but Bob was incorrect in the post he had made which you linked. TivaWare does not use AHB by default for TM4C123x devices, it uses APB by default.

    Best Regards,

    Ralph Jacobi

  • 0 in reply to Ralph Jacobi
    Prodigy 40 points

    Hi Ralph,

    thanks for your reply. Pretty embarrassing. I just realized that there are two "debug registers" in the Code Composer Studio. So if the AHB is activated I have to use the GPIO_PORTx_AHB if its deactivated the GPIO_PORTx register must be used. I assume this is due to different addressing.

  • +1 in reply to Johannes Lang
    TI__Guru*** 135355 points

    Hi Johannes,

    I wouldn't say that's embarrassing at all, it isn't very clear really! But yes, it is due to different addressing. Section 10.4 Register Map in the device datasheet outlines the addressing.

    Best Regards,

    Ralph Jacobi