TJA1100 RMII unused pins

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TJA1100 RMII unused pins

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pierrewatts
Contributor I

We use TJA1100 connected to a FPGA MAC where we evaluate both MII and RMII. MII works fine but RMII we have trouble transmitting data. Is there any specific requirements for how to treat unused MII pins e.g. TXD[2..3] etc?

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TomasVaverka
NXP TechSupport
NXP TechSupport

Hi Pierre,

In general, RMII requires 50 MHz/50 ppm crystal. Which parts have you chosen? Can you please share your schematic? To keep it confidential, please create a standart ticket.

Best regards,

Tomas

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pierrewatts
Contributor I

Hi Tomas,

We use the method in Fig6 of the TJA1100 datasheet "RMII signaling using an externally generated reference clock". The only difference is our clock source is an FPGA and not an oscillator, but its timing parameters are within spec.

We did manage to get it to work in the meantime so everything is fine, but we would still appreciate to know what NXP suggests one should do with the unused pins: high-Z, pulled up/down or hard driven high/low?

Regards,

Pierre

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