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Peripheral Architecture
2.2Signal Descriptions
Table 1 shows the MMC/SD controller pins that each mode uses. The MMC/SD protocol uses the clock, command
Table 1. MMC/SD Controller Pins Used in Each Mode
|
|
| Function |
| Type(1) | MMC and SD | SD |
Pin | Communications | Communications | |
CLK | O | Clock line | Clock line |
CMD | I/O | Command line | Command line |
DAT0 | I/O | Data line 0 | Data line 0 |
DAT1 | I/O | (Not used) | Data line 1 |
DAT2 | I/O | (Not used) | Data line 2 |
DAT3 | I/O | (Not used) | Data line 3 |
(1)I = input to the MMC controller; O = output from the MMC controller.
2.3Protocol Descriptions
The MMC/SD controller follows the MMC/SD protocol for completing any kind of transaction with the multimedia card and secure digital cards. For more detailed information, refer to the supported MMC and SD specifications in Section 1.5.
2.3.1MMC/SD Mode Write Sequence
Figure 5 and Table 2 show the signal activity when the MMC/SD controller is in the MMC/SD mode and is writing data to a memory card. The same block length must be defined in the MMC/SD controller and in the memory card before initiating a data write. In a successful write protocol sequence, the following steps occur:
∙The MMC/SD controller requests the CSD content.
∙The card receives the command and sends the content of the CSD register as its response.
∙If the desired block length, WRITE_BL_LEN value, is different from the default value determined from the response, the MMC/SD controller sends the block length command.
∙The card receives the command and sends responses to the command.
∙The MMC/SD controller requests the card to change states from standby to transfer.
∙The card receives the command and sends responses to the command.
∙The MMC/SD controller sends a write command to the card.
∙The card receives the command and sends responses to the command.
∙The MMC/SD controller sends a block of data to the card.
∙The card sends the CRC status to the MMC/SD controller.
∙The card sends a low BUSY bit until all of the data has been programmed into the flash memory inside the card.
SPRUE30B | Multimedia Card (MMC)/Secure Digital (SD) Card Controller | 13 |
