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RE: TM4C1294KCPDT: How to check the External oscillator and switch the clock source when main oscillator fail

Jay Wang_China
Prodigy 95 points
Other Parts Discussed in Thread: TM4C1294KCPDT

Hi Bob:

    I got a new issue is after  I select the PIOSC as clock source and cut off main oscillator signal , it would keep waiting SYSCTL_PERIPH_EPHY0 ready (use the function SysCtlPeripheralReady)when MCU initial the Ethernet module.

    I refer the data sheet of TM4C1294KCPDT, on page 1407,it describe that Ethernet Controller Module and Intergrated PHY recive two clock inputs. One is gated system clock and other is MOSC. As my personal opinion, does it means that Internal PHY  must be drive by MOSC ？ If so, this could explain why I cut off MOSC,  it would keep waiting the registet state ready,once I recover the MOSC signal,it could get through the initialization which even use PIOS as clock source.

  • 0
    TI__Guru**** 191886 points

    Hi,

      The ethernet PHY must use the MOSC. You must provide the 25MHz MOSC to the internal PHY for it to work. 

    ¡ The PHY receives the main oscillator (MOSC) which must be 25 MHz } 50 ppm for proper
    operation. The MOSC source can be a single-ended source or a crystal. Figure 20-2 on page 1410
    shows the clock inputs to the Ethernet Controller Module.