SPRUJB6B November 2024 – May 2025 AM2612
Coding Scheme for Command Token
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 13-182).
Figure 13-182 Command Token FormatCoding Scheme for Response Token
Response 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 MMC_CMD register must be configured differently to avoid false CRC or index errors to be flagged on command response (see Table 13-244). For more details about response types, see the Multimedia Card System Specification, the SD Memory Card Specification, or the SDIO Card Specification.
| Response Type MMC_CMD[17:16] RSP_TYPE(1) | Index Check Enable MMC_CMD[20] CICE | CRC Check Enable MMC_CMD[19] CCCE | Name of Response Type |
|---|---|---|---|
| 00 | 0 | 0 | No Response |
| 01 | 0 | 1 | R2 |
| 10 | 0 | 0 | R3 (R4 for SD cards) |
| 10 | 1 | 1 | R1, R6, R5 (R7 for SD cards) |
| 11 | 1 | 1 | R1b, R5b |
Figure 13-183 and Figure 13-184 depict the 48-bit and 136-bit response packets.
Figure 13-183 48-Bit Response Packet (R1, R3, R4, R5, R6)
Figure 13-184 136-Bit Response Packet (R2)Coding Scheme for Data Token
Data tokens always start with 0 and end with 1 (see Figure 13-185, Figure 13-186, Figure 13-187, and Figure 13-188).
Figure 13-185 Data Packet for Sequential Transfer (1-Bit)
Figure 13-186 Data Packet for Block Transfer (1-Bit)
Figure 13-187 Data Packet for Block Transfer (4-Bit)
Figure 13-188 Data Packet for Block Transfer (8-Bit)