Trouble Interfacing and Using SPI Flash Chips


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  1. #1
    Join Date
    Jan 2010
    Posts
    19

    Default Trouble Interfacing and Using SPI Flash Chips

    I have designed and had a circuit board built that interfaces an 18F2420 running at 5V to a 25VF032 SPI Flash.

    To allow the 2 voltages to mingle I am using a 74LVC126A in between as a level translator.

    The problem is that the PIC is not being able to drive the inputs of the level translator low enough to be a valid low.
    It's at about .81 volts which is above the maximum low for the 74 series part.

    I have tried voltage dividers using resistors instead of the chip solution with no success.

    I did notice that the Flash chip is sitting at about 2.9V on its SI and SCK pins with nothing connected.

    Does anyone have some experience with this and can offer ideas?

  2. #2
    Join Date
    Jan 2010
    Posts
    19

    Default Re: Trouble Interfacing and Using SPI Flash Chips

    Problem solved.
    74LVC126A was a bad part.
    Replaced it and still couldn't write the Flash.
    Turned out the Flash is write protected by default upon bootup.

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