We put 25MHz HSE to STM32F4, then forward same clock from MCO to micrel phy and then use micrels 50MHz for RMII. On Jul 2, 2013 8:50 PM, "Jeff Barlow" <j...@wb6csv.net> wrote:
> On 7/2/2013 4:50 AM, Claudius Zingerli wrote: > >> In the final design, we plan use a 3-port switch from Micrel. It can be >> clocked from 25MHz or 50MHz, but the board I'm using to develop the >> software has a DP83848 that does need a 50MHz clock source for RMII. >> STM32F4 /might/ be able to handle 50MHz as a main clock source. >> > > I see. For a one-off dev board I think it's always less frustrating to > just use a separate 50MHz oscillator. The older PHY chips can be really > fussy about clock jitter. I think once you get away from that DP83848 > you'll find things less painful. > > I was just suggesting using the Micrel RMII clock output to feed the RMII > clock input on the MCU. I've never tried feeding a 50MHz clock into the HSE > on a STM32F407 but it strikes me as risky. I do seem to recall that some of > the PHYs also have a direct 25MHz output that would work for that. Don't > know if that includes your switch chip, however. > -- > Later, > Jeff > > ______________________________**_________________ > lwip-users mailing list > lwip-users@nongnu.org > https://lists.nongnu.org/**mailman/listinfo/lwip-users<https://lists.nongnu.org/mailman/listinfo/lwip-users> >
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