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DM368 OSCCFG pin

Guru 15510 points

Hi

I have a question about DM368.

DM368 have "oscillator configuration" pin(OSCCFG)
which configure the range of oscillation frequency(MODE1 or MODE2).

I understood that I need to select the rang of oscillation via OSCCFG pin
when providing the clock from external xtal and DM368 internal oscillator.

When using external oscillator, do I also need to select the range of oscillator frequency via OSCCFG pin?
If yes, what will happen if OSCCFG pin are not configured appropriately?
For example, in our system, we are using external oscillator(24MHz) and we are using OSCCFG pin as GPIO and it is pulluped externally.
External pulled-up of OSCCFG pin means that the range of frequency is 30MHz - 45MHz.

best regards,
g.f.

  • Hi g.f,
    Please check your schematics that any peripheral using OSCCFG oscillator as source. If yes, you have to mux this pin as oscillator. Otherwise, you can use it as gpio.

    Thanks & Regards
    Bhargav
  • Hi Bhargav,

    Thank you for the reply.

    What is "OSCCFG oscillator" means?
    Is it internal oscillator circuit of DM368?

    As I mention above, we are using external oscillator as reference clock.
    And we are setting Mux OSCCFG pin as gpio and it is for external interrupt against DM368.

    best regards,
    g.f.
  • Hi g.f,
    As you mentioned, we can configure the range of oscillation frequency by using OSCFFG pin.

    When using external oscillator, do I also need to select the range of oscillator frequency via OSCCFG pin?
    yes. you have to select the range via OSCCFG pin.

    If yes, what will happen if OSCCFG pin are not configured appropriately?
    It may not work.

    Thanks & Regards,
    Bhargav
  • Hi Bhargav,

    I think this OSCCFG pin state will be latched at Power on Reset.
    So, is this OSCCFG pin need to be set to "0" or "1" at boot time only?
    And after the boot ends, it can be used as general purpose I/O(GPIO)?

    By the way, right now this OSCCFG pin are not configured appropriately at customer's board as I mentioned above.
    But the board seem its working fine. From your first reply,
    >Please check your schematics that any peripheral using OSCCFG oscillator as source. If yes, you have to mux this pin as oscillator. >Otherwise, you can use it as gpio.
    I thought this OSCCFG pin only need to be configured if internal oscillator has been used.
    So, I'm confusing now.
    Do you mean that OSCCFG pin must be configured, whether external or internal oscillator are used?

    best regards,
    g.f.
  • Hi g.f,
    OSCCFG pin configuration for external oscillator is optional.

    Thanks & Regards
    Bhargav
  • Hi Bhargav,

    Thank you for the relpy.
    I'm very sorry, but I can't understand.
    What do you mean that OSCCFG pin configuration is "optional" for external oscillator?
    I think you said it need to be configured when using external oscillator.
    Which answer is correct?

    We are using external oscillator(24MHz) and we are using OSCCFG pin as GPIO and it is pulluped externally.
    So, if range of frequency need to be configured via OSCCFG pin when using external oscillator,
    OSCCFG pin are not configured appropriately on the customer board.
    Can I leave this unappropriate configuration of OSCCFG pin, if it is optional for external oscillator?

    best regards,
    g.f.
  • Hi g.f,

    The OSCCFG configuration is optional.
    In DM368 data sheet, it mentions "Optionally, the oscillator inputs are configurable for use with external clock oscillators".
    For more info, please refer 6.6 section, 81 page.
    www.ti.com/.../tms320dm368.pdf

    Thanks & Regards,
    Bhargav
  • Hi Bhargav,
    "Optionally, the oscillator inputs are configurable for use with external clock oscillators".
    In this description of datasheet, it mentions that oscillator input which is MXI1 pin can be used as option for external clock oscillator.
    It's not mentioning that OSCCFG pin configuration is optional for external clock oscillator.

    Can you please search again.

    best regards,
    g.f.
  • Hi g.f,
    The oscillator input pins, MXI1, MXO, are designed to operate in two frequency ranges depending on the GIO81(OSCCFG) pin sampled at reset.

    Can you please refer section 3.7.6, page no.68 in the same document.

    Thanks & Regards,
    Bhargav.
  • Hi Bhargav,

    Thank you for the reply.
    Is section 3.7.6 of datasheet mentioning that oscillator input pins MXI1, MXO are deisgned to operate in two frequency ranges,
    whether external oscillator or internal oscillator are used?

    best regards,
    g.f.
  • Hi g.f,
    As per my understanding from the datasheet, incase of external oscillator,MXI1 will use OSCCFG configured frequency.
    Your understanding as per post (Oct 24, 2016 7:53 AM) is correct.Please configure OSCCFG as 0 for your oscillator frequency.(i.e. according to 3.7.6).Behaviour might be undefined if OSCCFG's configuration is inappropriate.

    Thanks and Regards,
    Bhargav