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SD card DET pin

oscargomezf

Hi everyone,

I'm working on a new design based on the PicoZed FMC Carrier Card V2. I'm considering using a micro SD card connector without insert card detection signal (DET).

In the schematic of the PicoZed FMC Carrier Card V2 is called SD_CD.

When the SD card detection is activated, the pins G3 and G4 are open and the SD_CD signal is high due to the pull-up resistor R68. If the SD card isn't inserted then the pins G3 and G4 are close and the SD_CD signal is GND.

What do I have to consider in the design?

Do I have to place a pull-up resistor to simulate that the SD card is always inserted?

Obviously, I only could insert the SD card when the system is power off. But It's not always going te be inserted an SD card.

 

Best regards.

  • 0

    Hi there,

    I'm not quite sure what you are trying to do.  You first mention that you want to not use the DET pin.  Then you go on to mention a few things that makes me think that you will sometimes have the memory there and sometimes not.

    Can I first ask, why don't you want to use the pin?

    You can certainly use pull-up or pull-down to set various states, however, you will be limiting what your system can do.  I would also like to point out that I am not aware of any SD Card cage that does not provide the appropriate signaling, which is why I asked above why you do not want to use that signal.  You make it seem that you ARE going to use an SD card cage, so this is confusing to me.

    --Dan

  • 0

    Hi zedman2000,

     

    Probably I have not explained very well. There are two types of micro SD card connector.

     

    i) The typical micro SD card connector push-push with card detect: http://katalog.we-online.de/em/datasheet/693071010811.pdf

    ii)  The micro SD card connector Hinge: http://katalog.we-online.de/em/datasheet/693072010801.pdf

     

    I would like to use the micro SD card connector Hinge, but this type of connector doesn't have SD_DET pin because you can't  extract the sd card pushing it.

    So If I use this type of SD card connector, I don't know if I have to place a pull-up resistor to simulate that the SD card is always inserted (When the card is inserted the switch is open and regarding to the schematic of the PicoZed FMC carrier V2, and due to the R68 pull-up resistor, the input SD_CD of the host (picoZed) is high.

     

    https://www.dropbox.com/s/ttxuorho07hdzzy/PicoZed_FMC_Carrier_V2_SD_CARD.png

     

    Do you know what I mean?

     

    Best regards.

  • 0

    Hi there,

    I checked with a few colleagues.  From what our experience has shown, you should be able to control that line internal to the Zynq.  As I understand it, we actually used to do this pre-2015.2.  From what was explained to me, you actually can control the CD and WP lines without the need for external straps.

    My suggestion is to put pads for the lines that you can.  You can always not-populate them for your design and use the internal mechanisms.

    --Dan