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Altera_Forum
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12 years ago

Pull up & pull down resistots on MSEL pins in Cyclone-IV E

Dear sir,

This is regarding connecting MSEL pins to VCCA & GND using pull-up/pull-down resistors respectively.

In Cyclone -IV handbook it is suggested as

"Hardwire the MSEL pins to VCCA or GND without pull-up or pull-down resistors to

avoid problems detecting an incorrect configuration scheme. Do not drive the MSEL

pins with a microprocessor or another device."

But in reference design of Cyclone-IV GX c4gx_f896.pdf, they used 10K value resistors as pull-up & pull-down resistors on MSEL pins.

Do I need to connect '10K ohm resistors to MSEL pins before connecting to VCCA & GND ? Or can I directly connect MSEL pins to VCCA & GND without any resistors ?

Regards,

Thulasi

1 Reply

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    12 years ago

    There are some inconsistencies between Altera's documentation and a number of their own (and partner) development kits.

    If you know which configuration scheme you are going to use I recommend connecting the MSEL pins directly to GND or VCCA. Remember, you will always have configuration via JTAG available, regardless of the hard wired configuration scheme you chose.

    If you do need options (to chose between different configuration schemes) I suggest using 0R resistors.

    Finally, many people (including myself) have had success driving the MSEL pins from a microcontroller or similar. Providing the MSEL pins are stable at the point at which they are sampled (ensure they are stable when you release nCONFIG), you are unlikely to see any problems.