Figure 20-2 shows the
SDMMC host controllers connected to an SD card and its related external
connections.
Figure 20-2 shows the
SDMMC host controller connected to an SD card and its related external connections.
The following SDMMC pins are used
- SDMMC_CMD This pin is used for two-way communication between the
connected card and the SDMMC. The SDMMC transmits commands to
the card and thememory card drives responses to the commands on this pin.
- SDMMC_DAT3-0 Depending on
which type of card you are using, you may need to connect 1 or 4 data lines. The
number of DAT pins (the data bus width) is set by the Data Transfer Width (DTW)
bit in the SDMMC control register (SD_HCTL). For more information, see Section 20.4
- SDMMC_CLK This pin provides the clock to the memory card from the SD
controller.
- SDMMC_POW Used for SD card's cards on/off power supply control. When
high, denotes power-oncondition.
- SDMMC_CD This input pin serves as the SD carrier detect. This signal is
received from amechanical switch on the slot.
- SDMMC_WP This input pin is used for the SD card's write protect. This
signal is received from amechanical protect switch on the slot (system
dependant). Applicable only for SD cards that have a mechanical sliding tablet
on the side of the card.
Note: The SDMMC_CLK pin functions as an output but must be
configured as an I/O to internally loopback the clock to time the inputs.
Table 20-5 provides a
summary of these pins.
Table 20-5 SDMMC Pins and Descriptions
| Pin |
Type |
1-Bit Mode |
4-Bit Mode |
Reset Value |
| SDMMC_CLK(1) |
O |
Clock Line |
Clock Line |
0 |
| SDMMC_CMD |
I/O |
Command Line |
Command Line |
1 |
| SDMMC_DAT0 |
I/O |
Data Line 0 |
Data Line 0 |
1 |
| SDMMC_DAT1 |
I/O |
(not used) |
Data Line 1 |
1 |
| SDMMC_DAT2 |
I/O |
(not used) |
Data Line 2 |
1 |
| SDMMC_DAT3 |
I/O |
(not used) |
Data Line 3 |
1 |
(1) The SDMMC_CLK pin functions as an output but must be configured as an I/O to
internally loopback the clock to time the inputs.