Go Down

Topic: Do SD cards ever need CMD1? (Read 134 times) previous topic - next topic

ShermanP

I'm working on an SD card bootloader for, uh, another processor, and have it working for SD cards, but not SDHC.  I'm working against a code size limit, and if I modify the code to support SDHC, I have to save bytes somewhere.  One thing that I currently have is the CMD1 command, which I get to if ACMD41 returns "illegal command".  But the more I read about this, including a flowchart from the SD Association, it appears that CMD1 was originally an MMC command, and while version 1 SD cards responded to that command, none of them really needed it.  In other words, it looks like all SD cards, even version 1, respond to ACMD41.  Can anyone confirm that?  CMD1 appears nowhere on the flowchart.

Another question in case anyone knows.  The CMD58 command response is R3, which is an R1 followed by four bytes of register contents.  But I can't find the expected R1 response if the command is successful.  Should I be looking for a zero or a one?


Go Up