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System behavior when oscillator short to Ground

Abhijeet Mutha1
Prodigy 120 points
Other Parts Discussed in Thread: TMS570LS0332

Hi ,

We are using TMS570ls0332 micro controller in our project.

Following is the experiment performed by us:

1) Short the External oscillator pin ( OSCIN) pin with GND(Ground).

2) Change the oscillator frequency runtime from 8MHz to 10MHz and 8MHz to 7MHz.

Following are the observed behavior of the system in both the experiment .

1) The system immediately jumped to Tri-state( get stuck) , with the help of J-TAG debugger i can see that the execution has jumped to 0x00000000 location and no further execution is taking place (Even after removing OSCIN pin short to GND  or resuming previous clock frequency i.e. clock signal is resumed ).

2) The External watchdog is trying to restart the system by giving a 'LOW' signal to nRST pin , but action is taken by the system ( System is not get restart).

Can you please explain if this behavior is as expected ? 

we have enabled the PLL slip , thus we expect to get the PLL slip error notification .

 Thanks and Regards

  • 0
    TI__Mastermind 22715 points
    You observed reset because of the value you programmed in the SYS.PLLCTL1 register. Please check the value in your test and refer to TRM for more details about this register.

    Thanks and regards,

    Zhaohong
  • 0 in reply to Zhaohong Zhang
    Prodigy 120 points
    Dear Zhaohong,

    As i mentioned previously , the system is NOT GETTING RESET ....

    The execution jumps to 0x00000000 location and no further operation takes place i.e. the system gets stuck.

    Below is the value we programmed in SYS.PLLCTL1.

    SSYSTEMREG1->PLLCTL1 = (ULONG)0x80000000u
    /** By pass on PLL slip <-- enabled*/
    | (ULONG)0x20000000u
    /** Setup R PLL divider to Max*/
    | (0x1Fu<< 0x00000018U)
    /** Reset on PLL slip <-- disable*/
    | (ULONG)0x00800000u
    /** NR (REF_CLK_DIV) <-- 4*/
    | ((4u - 1u)<< 0x00000010U)
    /** NF (PLL_MUL) <-- 120 */
    | ((120u - 1u)<< 0x00000008u);

    Can you please help me with the expected system behavior with above programmed value.
  • 0 in reply to Abhijeet Mutha1
    TI__Mastermind 22715 points
    Program counter stuck at the address 0x0 indicates that there is continuous reset. You can use a scope to monitor the nRST pin. You PLLCTL1 setting will cause a reset for PLL and OSCIN error. Please check TRM for more details.

    Thanks and regards,

    Zhaohong