It's my first time to design the micro SD reader circuit. I hope that my design can support micro SD card with various speed class(from class2 to class10). According to my understanding, the only difference for different speed class is the clock frequency from a circuit perspective. Does my guess correct? Or are there other things should be concern about when designing a circuit for various speed class? Since the clock source is the CPU peripheral interface in my design, so if I don't change the clock frequency, does a class2 card has the same data rate as a class10 card?