alt_up_sd_card_open_dev return 0. Whats wrong??

Hallo,

I try to use the SD-Card IP from the University Proram and have implement the ip into my nios II System in sopc builder.

If I try to use the function

alt_up_sd_card_open_dev(SD_CARD_NAME)

it returns always zero.

What did I wrong? Can everybody help me?

Another Question is, what is the Maximum size of the sd Card I can use with the University program?

Thanks