Honored ContributorSD/MMC cards are supposed to support hot-plug and live insertion. But I don't see any kind of protection on the SD connector. It is the same on all the Altera/Terasic DE boards.
I know the pins are arranged for the corrector contact order. But is this enough? Shouldn't be some diode protection on the board?
Honored ContributorHello,
from the MMC specification: --- Quote Start --- If hot insertion feature is implemented in the host, than the host has to withstand a shortcut between VDD and VSS without damage. --- Quote End --- With Terasic DE1 and DE2, VDD ist directly connected to 3.3V supply, I guess the quoted condition isn't met. You could conclude, that these Boards thus don't implement hot plugging. But I would worry about for a retail product, not for an evaluation board. I'm also in doubt, if typical consumer products care about MMC spec. For an industrial product, I would recommend a current limiter for VDD and protection diodes at data lines. I won't be sure, if e. g. supply contact lead is enough to prevent from ESD hitting a data line during card insertion. Regards, FrankHonored ContributorThanks Frank,
I also wonder what kind of protection consumer devices have. And I'm tempted to open a card reader to see what's in there.Honored ContributorHello,
card readers most likely utilize application specific devices that may have more effective internal protection than an FPGA.
