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Can TMS570 run with PLL VCC disconnected?

Richard Burke
Expert 1910 points
Other Parts Discussed in Thread: TMS570LS3137

Hello,

We have prototyped a new board with a TMS570LS3137. Unfortunately the PLL VCC  pin was connected to the wrong supply rail. The hardware guys have managed to disconnect the pin but have been unable to connect to the correct voltage. Before they re-spin the board they want to be sure there are no other problems.

The TMS570 has various clock sources. Can the processor run with the PLL VCC pin disconnected?

I tried to connect with a XDS510 USB JTAG interface. The board responds correctly to the test connection script but I can't make it connect. Is it possible to debug using the crystal or one of the internal oscillators only? If so, is there a setting I need to change in the debug configuration?

Thanks,
Richard 

  • 0
    TI__Guru 59540 points

    Hi Richard,

    I have forwarded your post to one of our PLL/internal clocking experts. They should get back with you in a short while.

  • 0 in reply to Chuck Davenport
    Expert 1910 points

    Thanks Chuck. I'm not sure if it is relevant but the warm reset (nRST) responds correctly to a power on reset (nPORRST) and as stated above the scan chain diagnostic in CCS reports that it can see the device (see below). However when I connect I get error 0x80000240/-5005.

    Thanks,
    Richard

  • 0 in reply to Richard Burke
    TI__Mastermind 20030 points

    Richard,

    The PLL cannot be run without the PLLVCC connected. However, the part should be active; "should be" is dependent upon the software. If you are setting reset on slip or reset of oscillator failure, you may have some difficulty; also if the PLL is used before it is enabled... You could try this:

    - short or remove the crystal from the board. This will trigger an oscillator failure. Assuming that the code does not force a reset on oscillator failure, the device will clock from the internal low power oscillator (roughly 10MHz). This might allow you to connect via JTAG...

    Best of luck.

    Kevin

  • 0 in reply to Kevin Lavery
    Expert 1910 points

    Hi Kevin,

    Thanks for the response. The board we are trying to connect to is unprogrammed so I am assuming that the clock sources are set to their default values. According to the datasheet the main oscillator, the LFO and the HFO are enabled and nothing else. I don't know whether the XDS510 JTAG interface manages to load any code but I suspect not.

    I will try your suggestion of disconnecting the crystal and will let you know the results.

    Regards,
    Richard