Texas Instruments TMS320DM644x manual Signal Descriptions, Protocol Descriptions

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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 (two-way communication between the MMC controller and memory card), and data (DAT0 for MMC card, DAT0-3 for SD card) pins.

Table 1. MMC/SD Controller Pins Used in Each Mode

			Function
	Type(1)	MMC and SD (1-bit mode)	SD (4-bit mode)
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 –September 2006 Multimedia Card (MMC)/Secure Digital (SD) Card Controller 13

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