EK-TM4C123GXL: The system cannot work when changing a system clock setting

Hello Depeng,

The images you tried to post did not load correctly.

Also if this is specifically about the EK-TM4C123GXL - neither of those should work because the board is populated with a 16MHz crystal so you need to make sure the SYSCTL_XTAL parameter reflects that:

    //
    // Set the system clock to run from the PLL at 80MHz.
    //
    SysCtlClockSet(SYSCTL_SYSDIV_2_5 | SYSCTL_USE_PLL | SYSCTL_OSC_INT |
                       SYSCTL_XTAL_16MHZ);

That runs from the PLL.

    //
    // Set the clocking to run directly from the crystal.
    //
    SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_MAIN |
                       SYSCTL_XTAL_16MHZ);

This alternatively runs from the crystal itself.

Best Regards,

Ralph Jacobi