3.4.6.1 SDMMC1 Connector
A 4-bit small-size microSD card connector, J42, connected to the SDMMC1 interface, is mounted on the top side of the board. The SDMMC1 communication is based on an 8-pin interface (clock, command, four data and power lines). It includes a card detection and write-protect switch.
The SDMMC1 connector enables the system to boot from an SD card, provided that the correct binary file is copied to the root level of the card.
The SDMMC reset is triggered by the system reset signal, which cycles the SD card power using the MIC94085YFT high-side load switch. For more information about the MIC94085YFT device, refer to the product web page.
|
PIO |
Signal Name |
Signal Description |
|---|---|---|
|
PB30 |
SDMMC1_0.SDMMC_1V8SEL |
1.8V/3.3V voltage selection |
|
PB29 |
SDMMC1_0.SDMMC_CD |
SD card detection |
|
PB23 |
SDMMC1_0.SDMMC_CLK |
SDIO clock |
|
PB22 |
SDMMC1_0.SDMMC_CMD |
SDIO command |
|
PB24 |
SDMMC1_0.SDMMC_DATA0 |
SDIO data bit 0 |
|
PB25 |
SDMMC1_0.SDMMC_DATA1 |
SDIO data bit 1 |
|
PB26 |
SDMMC1_0.SDMMC_DATA2 |
SDIO data bit 2 |
|
PB27 |
SDMMC1_0.SDMMC_DATA3 |
SDIO data bit 3 |
The SDMMC1 interface supports switching the I/O voltage level from 3.3V to 1.8V to enable High-Speed modes for the SD card.
When jumper JP18 is set across pins 2-3 of header J45, the SAMA7D65 MPU can control switching dynamically by asserting the PB30 PIO high (selecting 1.8V) if a card supporting High-Speed modes is detected (depending on software support).
When jumper JP18 is set across pins 1-2 of header J45, the 3.3V (legacy speeds) is permanently selected.
The schematic below shows the circuit that selects the 3.3V or 1.8V voltage using the TPS2117DRLR power multiplexer.