Post by thread:[PIC]: Puzzling MMC read failure

Working with an MMC, here's what I do: Initialize: CMD0, delay, response 0x01 CMD1, delay---loop until response 0x00, response 0x00 Then, I send the card read command with address 0000 0000, i.e. CMD17. I should be getting 0x00 after delay and then 0xFE after delay as the start data token. If there was a failure with the command, I should be getting a standard R1 error byte. Instead, after sending CMD17, here's what I get in the next couple response bytes: 0xFF (expected) 0xFE (??!!!; 0x00 skipped) 0x03 (R1 or data error token? If data error token, what would both "Error" and "CC controller" error mean?) 0xFF 0xFF 0xFF 0xFF 0x0B (R1 or data error?) 0xFF.....continuously The card works perfectly well in a USB reader for both read/write. Any clues? Thanks, Ishaan -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

You don't mention sending a crc; isn't one required? Tom M. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

In SPI mode, a CRC is only required for the reset (CMD0) command, which initializes the card in SPI mode. By default, CRC is disabled in SPI mode, and a dummy CRC byte (byte 6 of 6 in each command) of FFh is sent with each command. Cheers, Ishaan {Original Message removed}