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TRF7964A: Regarding crystal setting

Toshimitsu Tanaka
Prodigy 30 points
Part Number: TRF7964A


Regarding main crystal(external),it seems that 13.56-MHz or 27.12-MHz crystal can be used, and the data sheet says that the 13.56-MHz or 27.12-MHz crystal (or oscillator) is controlled by the Chip Status Control
register (0x00) and the EN and EN2 terminals.

When we use 27.12MHz crystal, which bit in Chip Status Control register (0x00) needs to be set?

Or Modulator and SYS_CLK Control Register (0x09) is related to the setting?
(B4/B5 bit seems to be setting for clock output...)
(What B7 bit stands for actually? I could not understand the definition..)

I am just wondering how the device（TRF7964A) is configured for external clock.

Could you please let me know?

  • +1
    TI__Mastermind 24660 points

    Hello Toshimitsu,

    I agree, the data sheet is a little misleading regarding crystal control via Chip Status Control register (0x00).

    The selection between 13.56 MHz or 27.12 MHz is done in SYS_CLK Control Register (0x09) with bit B7. This bit is enabled by default, so the 27.12MHz crystal mode is automatically selected. B4 / B5 are controlling the divider (by 1, 2, or 4) for the external SYS_CLK signal at pin 27.

    An external clock oscillator source can be connected to pin 31 to provide the system clock alternativelly; pin 30 can be left open. No special configuration is required.

    Best regards,

    Andreas.

  • 0
    Prodigy 30 points

    Understood. Thank you very much.