What is the purpose of R667 in the Sabre schematics

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What is the purpose of R667 in the Sabre schematics

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dougschwanke
Contributor IV

I understand that this is a DNP part, but I am wondering why the part was even on the schematic.  We have a lot of customers who replicate this design and are placing pads on the board.

When would someone pull this pin down? 

My current assumption is that it is related to designs where the user uses 4 data lines and DAT3/CD share the same pin, such as micro SD cards.

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dougschwanke
Contributor IV

Based on http://www.nxp.com/documents/application_note/AN10911.pdf [^] page 17, the Micro SD card has built in pullup resistor on CD/D3 pin (10Kohm - 90Kohm).

NXP recommended an external pull-down resistor should be 270Kohm or higher.  Since the Sabre schematic (SPF-27392_C3) lists 10K, I have ask if this has ever been tested in the lab.

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dougschwanke
Contributor IV

Populating this resistor did not fix our problem of Linux detecting the 4-bit interface. 

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