Connecting Ehternet PHY to OMAP-L13x

Prad

Expert 1125 points

Other Parts Discussed in Thread: OMAP-L137

Hi,

Is it necessary to use a buffer between the Ehternet PHY and OMAP-L13x ?

According to the OMAP-L137 EVM's schematic here, the PHY KSZ8893MQL is connected to OMAP through

a Bus Exchange switch(SN74CBTLV16212DGGR).

According to the datasheet of KSZ8893(Page 103),

with regards to PHYs SNI Transmit to OMAP the Ouput Valid minimum time is "0ns"

On the other hand regarding the OMAP's (MDIO_CLKH-MDIO)- Hold time,

the datasheet(Page 108-109) of OMAP-L13x mentions that, MDIO_D data input valid after MDIO_CLK high min i.e th(MDIO_CLKH-MDIO) = 10 ns.

Please let me know whether we should have a 10ns buffer between the PHY and OMAP (EVM doesn't implement such delay logic).

Thankyou in advance

Regards.

over 15 years ago

0 tlee over 15 years ago

TI__Guru 62975 points

Prad,

A buffer is typically not necessary. The timings for the optional MDIO interface are independent from the functional EMAC interface.

-Tommy

0 Prad over 15 years ago in reply to tlee

Expert 1125 points

Hi Tommy,

Thankyou,

I couldn't understand, could you please show me any documents or application note about connecting

Ethernet PHY to OMAP-l13x,

I am confused that PHY will transmit with 0 ns hold time but as per device(OMAP), it need 10 ns hold time .

Regards,

0 tlee over 15 years ago in reply to Prad

TI__Guru 62975 points

Prad,

In the KSZ8893 datasheet, page 103 is for SNI (7-wire serial network interface), whereas the MDIO interface is referred to by the datasheet as MIIM (MII management interface). I think the MDIO timings are defined in the IEEE spec.

-Tommy

0 Prad over 15 years ago in reply to tlee

Expert 1125 points

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Connecting Ehternet PHY to OMAP-L13x