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BF527 Ethernet with LAN8720 RMII Phy

Question asked by tcmichals on Jan 25, 2011
Latest reply on Feb 3, 2011 by tcmichals

The LAN8700 Ethernet phy is not recommended for new designs and I'm looking aty the new LAN8720 RMII and what etherent driver changes.

 

I see one, which is the PHY ID needs to be updated, no issue

 

I'm confused about the MDC timing value.  Looking at the driver, CLKIN is 25 ie 25Mhz, so, I'm confused if a RMII clock is 50Mhz, no 25Mhz.

u32 fcclk,fsclk,fvco;
            u32 N,mdc;

 


            vco = ((*pPLL_CTL>>9)&0x3f) * dev->CLKIN;
            if (*pPLL_CTL&1) {
                vco = vco>>1;   // divide by 2
            }
            cmsel = (*pPLL_DIV>>4)&0x3;
            fcclk = vco/(1<<cmsel);

 

            cmsel = *pPLL_DIV&0x0f;
            fsclk = vco/cmsel;

 

            N= (((fsclk+4)/5)-1)&0x3f;

 

            mdc = (fsclk*5)/(N+1);

 

So does this need to change?

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