www.ti.com
Functional Description
Figure 18-5 shows the MMC/SD/SDIO0 host controller connected to an MMC, SD, or SDIO card and its
related external connections. Note that MMC/SD/SDIO0 uses the same signals as MMC/SD/SDIO1 and 2
but adds MMC_POW.
The following MMC/SD/SDIO controller pins are used
• MMC_CMD This pin is used for two-way communication between the connected card and the
MMC/SD/SDIO controller. The MMC/SD/SDIO controller transmits commands to the card and the
memory card drives responses to the commands on this pin.
• MMC_DAT7-0 Depending on which type of card you are using, you may need to connect 1, 4, or 8
data lines. The number of DAT pins (the data bus width) is set by the Data Transfer Width (DTW) bit in
the MMC control register (SD_HCTL). For more information, see Section 18.5.1, MULTIMEDIA_CARD
Registers.
• MMC_CLK This pin provides the clock to the memory card from the MMC/SD controller.
• MMC_POW Used for MMC/SD card's cards on/off power supply control. When high, denotes power-on
condition.
• MMC_SDCD This input pin serves as the MMC/SD/SDIO carrier detect. This signal is received from a
mechanical switch on the slot.
• MMC_SDWP This input pin is used for the SD/SDIO card's write protect. This signal is received from a
mechanical protect switch on the slot (system dependant). Applicable only for SD and SDIO cards that
have a mechanical sliding tablet on the side of the card.
Note: The MMC_CLK pin functions as an output but must be configured as an I/O to internally
loopback the clock to time the inputs.
Table 18-7 provides a summary of these pins.
Table 18-7. MMC/SD/SDIO Controller Pins and Descriptions
Pin Type 1-Bit Mode 4-Bit Mode 8-Bit Mode Reset Value
MMC_CLK
(1)
O Clock Line Clock Line Clock Line High impedance
MMC_CMD I/O Command Line Command Line Command Line High impedance
MMC_DAT0 I/O Data Line 0 Data Line 0 Data Line 0 0
MMC_DAT1 I/O (not used) Data Line 1 Data Line 1 0
MMC_DAT2 I/O (not used) Data Line 2 Data Line 2 0
MMC_DAT3 I/O (not used) Data Line 3 Data Line 3 0
MMC_DAT4 I/O (not used) (not used) Data Line 4 0
MMC_DAT5 I/O (not used) (not used) Data Line 5 0
MMC_DAT6 I/O (not used) (not used) Data Line 6 0
MMC_DAT7 I/O (not used) (not used) Data Line 7 0
(1)
The MMC_CLK pin functions as an output but must be configured as an I/O to internally loopback the clock to time the inputs.
18.3.1.2 Protocol and Data Format
The bus protocol between the MMC/SD/SDIO host controller and the card is message-based. Each
message is represented by one of the following parts:
Command: A command starts an operation. The command is transferred serially from the
\MMC/SD/SDIO host controller to the card on the mmc_cmd line.
Response: A response is an answer to a command. The response is sent from the card to the
MMC/SD/SDIO host controller. It is transferred serially on the mmc_cmd line.
Data: Data are transferred from the MMC/SD/SDIO host controller to the card or from a card to the
MMC/SD/SDIO host controller using the DATA lines.
Busy: The mmc_dat0 signal is maintained low by the card as far as it is programming the data received.
3351
SPRUH73H–October 2011–Revised April 2013 Multimedia Card (MMC)
Submit Documentation Feedback
Copyright © 2011–2013, Texas Instruments Incorporated
To Next Page
Loading...
Need help?
General
