U-Boot > mmc dev 0
CMD_SEND:0
                ARG                      0x00000000
 RET: 0 , 0x0
                MMC_RSP_NONE
CMD_SEND:8
                ARG                      0x000001AA
 RET: -19 , 0xffffffed
                MMC_RSP_R1,5,6,7         0x2FF67610
CMD_SEND:55
                ARG                      0x00000000
 RET: -19 , 0xffffffed
                MMC_RSP_R1,5,6,7         0x2FF67610
CMD_SEND:0
                ARG                      0x00000000
 RET: 0 , 0x0
                MMC_RSP_NONE
CMD_SEND:1
                ARG                      0x00000000
 RET: -19 , 0xffffffed
                MMC_RSP_R3,4             0x00000000
Card did not respond to voltage select!

U-Boot > mmc dev 1
MMC: no card present