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LPC1769 and PHY DP83848 clock synchronization via CLKOUT pin

Question asked by Javier Cambiasso on Jun 6, 2019
Latest reply on Jun 18, 2019 by Javier Cambiasso

Hello, I currently designing a custom board for the LPC1769 with Ethernet connectivity. I know the DP83848 PHY is kinda old but is the only CMSIS-CORE compatible PHY chip I have cheaply and readily available in my country. 

 

The PHY needs an external clock source of 50Mhz to operate in RMII mode so I was wondering if I could use the LPC1769 clock out pin to generate this signal. I found an old schematic for the RBD1768 board using the same PHY chip and they used an external clock generator. I would like to keep the hardware components count as low as possible so again, why not use the CLKOUT pin? Correctly configured in firmware of course.

 

Also, I would have to connect the CLKOUT pin to the ENET_REF_CLK of the 1769, am I correct? Or is it not necessary?

 

Thanks.

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