SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
Coding Scheme for Command Token
Command tokens always start with 0 and end with 1. The second bit is a transmitter bit: 1 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 27-7).
Coding Scheme for Response Token
Response tokens always start with 0 and end with 1. The second bit is a transmitter bit: 0 for a card response. The content is different for each type of response (R1, R2, R3, R4, and R5, R6, R7 [for SD]) and the content is protected by 7-bit CRC checksum (see Figure 27-8 and Figure 27-9). Depending on the type of commands sent to the card, the MMCHS_CMD register must be configured differently to avoid false CRC or index errors to be flagged on command response (see Table 27-4). For more information about response types, see the Multimedia Card System Specification, SD Memory Card Specifications, and SDIO Card Specification.
Response Type MMCi.MMCHS_CMD[17:16] RSP_TYPE | Index Check Enable MMCi.MMCHS_CMD[20] CICE | CRC Check Enable MMCi.MMCHS_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 |
Coding Scheme for Data Token
Data tokens always start with 0 and end with 1 (see Figure 27-10 through Figure 27-12).