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DRA821U: DRA821U C16 pin function

Bard Ciou
Intellectual 900 points
Part Number: DRA821U
Other Parts Discussed in Thread: DRA821, LMK1C1104

Dear ,

about the system design of DRA821U.

  • C16Pin output the 25Mhz frequency and connect to ethernet phy. how could DRA821U provide the 25mHZ internally (thru internal OSC)?
  • Could C16Pin connect to multiple ethernet phy protocol?
  • If the external 4 ports of CPSW5G are connected to four pair 1000Base-T1 phy. could these 4 pairs can use same MCU_CLKOUT0 and C16 pin of DRA821?

Regards,

bARD 

  • 0
    TI__Guru 51785 points

    Are you asking how to setup/program the device to generate 25MHz clock?  See register CTRLMMR_MCU_CLKOUT0_CTRL register in TRM, there is bit to enable clock and bit to select between 25 and 50Mhz.  The proper pin-mux settings will also be required.  If required for booting, there are also boot mode options to select the specific clock by default.

    If asking out best to connect single clock source to multiple PHYs?  A clock buffer can be used to keep the clock edges sharp/eliminate signal integrity issues.. See Ti.com and search for Clock Buffers.  Example might be LMK1C1104.