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AM335x AHCLKR or AHCLKX required?

Daniel Weiss26
Prodigy 30 points

Is it true that for the I2S mode the AHCLKR (or AHCLKX) clocks are not required unless the corresponding bitclock is generated from those clocks?

Daniel

  • 0
    TI__Guru**** 161600 points
    Hi Daniel,

    Yes, reference clocks may be sourced from an external clock: ACLKX or ACLKR pins. To select the transmit clock to be externally sourced from ACLKX pin, you need to configure the ACLKXCTL[5]CLKXM = 0x0. To select the receive bit clock to be externally sourced from ACLKR pin set ACLKRCTL[5]CLKR = 0x0

    Detailed description of this is presented in Section 22.2.5 Clock and Frame Sync Generators.

    Best Regards,
    Yordan
  • 0 in reply to Yordan Kovachev
    Prodigy 30 points
    Thank you, Yordan. So if I feed the ACLKX and ACLKR from an external clock then the AHCLKR and AHCLKX signals are not required?
    Daniel
  • 0 in reply to Daniel Weiss26
    TI__Guru**** 161600 points
    Hi Daniel,

    "The transmit bit clock, ACLKX, (Figure 22-16) may be either externally sourced from the ACLKX pin or internally generated, as selected by the CLKXM bit. If internally generated (CLKXM = 1), the clock is divided down by a programmable bit clock divider (CLKXDIV) from the transmit high-frequency master clock (AHCLKX)."

    So, yes, when you use external clock as a source for your transmit bit clock, you don't need the PRCM related configuration and clock divider settings for AHCLKX.
    See Figure 22-16. Transmit Clock Generator Block Diagram, if external source is selected for the transmit bit clock CLKXM=0x0 it is fed directly from ACLKX pin.

    Best Regards,
    Yordan
  • 0 in reply to Yordan Kovachev
    Prodigy 30 points
    Hi Yordan
    Yes, right. I just wanted to make sure that the AHCLKX (or AHCLKR) signals are not required for anything else. I think it is not that obvious in the TRM.
    Thank you!
    Daniel