MultiMediaCard Protocol - USB Mass Storage: Designing and Programming Devices and Embedded Hosts - page 111

In a command's first byte, bit 7 = 0, bit 6 = 1, and bits 5..0 are the command
index. In other words, the first byte in the command equals the command
index + 40h.
The code below provides values for the first bytes in MultiMediaCard com-
mands:
// command first byte command index
#define cmdGO_IDLE_STATE 0x40 // 0

#define cmdSEND_OP_COND 0x41 // 1

#define cmdSEND_CSD 0x49 // 9

#define cmdSEND_CID 0x4a // 10

#define cmdSTOP_TRANSMISSION 0x4c // 12

#define cmdSEND_STATUS 0x4d // 13

#define cmdSET_BLOCKLEN 0x50 // 16

#define cmdREAD_SINGLE_BLOCK 0x51 // 17

#define cmdREAD_MULTI_BLOCK 0x52 // 18

#define cmdWRITE_SINGLE_BLOCK 0x58 // 24

#define cmdWRITE_MULTI_BLOCK 0x59 // 25

#define cmdTAG_SECTOR_START 0x60 // 32

#define cmdTAG_SECTOR_END 0x61 // 33

#define cmdUNTAG_SECTOR 0x62 // 34

#define cmdTAG_ERASE_GRP_START 0x63 // 35

#define cmdTAG_ERASE_GRP_END 0x64 // 36

#define cmdUNTAG_ERASE_GRP 0x65 // 37

#define cmdERASE 0x66 // 38

#define cmdSD_APP_OP_COND 0x69 // 41

#define cmdLOCK_UNLOCK 0x71 // 49

#define cmdAPP_CMD 0x77 // 55

#define cmdREAD_OCR 0x7a // 58

#define cmdCRC_ON_OFF 0x7b // 59