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USB Superspeed Peripherals

Anonymous
Not applicable

Hello,

   

I got two questions about the FX3 GPIOs.

   

What should I do with unused GPIO pins in my design ? Should I leave it floating ?

   

My second question is about the 22Ohms resistor. In the datasheet it is said that a 22Ohm should be connected to any pin driven by the GPIFII interface. I thought that any other pin should not be connected to that resistor but I saw in the Superspeed explorer kit schematics that a 22Ohm resistor is also connected to the UART and SPI pins. What should I do ?

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Anonymous
Not applicable

Yes, you can leave the pins floating if you do not use it. 

   

It is not necessary to provide 22 ohms on the UART/SPI lines. WE recommend using 22-Ω series termination resistors to avoid reflection on GPIF lines 

   

 

   

Please refer the app note for more: http://www.cypress.com/file/139936/download

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New Contributor

My FX3 lanes run ~0.7" long straight in to the FPGA. Do you still see a need for the 22 ohm resistors? Not a big deal adding them but adds work. Thank!

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