SWRU626 December 2025 CC3501E , CC3551E
Command packets always start with 0 and end with 1. The second bit is a transmitter bit1 for a host command. The content is the command index (coded by 6 bits) and an argument (for example, an address), coded by 32 bits. The content is protected by 7-bit CRC checksum (see Figure 20-5).
Figure 20-5 Command
Token FormatResponse packets always start with 0 and end with a 1. The second bit is a transmitter bit0 for a card response. The content is different for each type of response (R1, R2, R3, R4, R5, and R6) and the content is protected by 7-bit CRC checksum. Depending on the type of commands sent to the card, the SD_CMD register must be configured differently to avoid false CRC or index errors to be flagged on command response (see Table 20-6). For more details about response types, see the SD Memory Card Specification.
| Response Type SD_CMD[17:16] RSP_TYPE | Index Check Enable SD_CMD[20] CICE | CRC Check Enable SD_CMD[19] CCCE | Name of Response Type |
|---|---|---|---|
| 00 | 0 | 0 | No Reponse |
| 01 | 0 | 1 | R2 |
| 10 | 0 | 0 | R3, R4 |
| 10 | 1 | 1 | R1, R6, R5, R7 |
| 11 | 1 | 1 | R1b, R5b |
Figure 20-6 and Figure 20-7 depict the 48-bit and 136-bit response packets.
Figure 20-6 48-Bit
Response Packet (R1, R3, R4, R5, R6)
Figure 20-7 136-Bit
Response Packet (R2)
Figure 20-8 Data
Packet for Block Transfer (1-Bit)
Figure 20-9 Data
Packet for Block Transfer (4-Bit)