Table 23: 4bit SD/MMC/SDIO signals
2.13.2 Reference Schematics
Even if the selected module does not require pull-up resistors on the data and command lines, it is
recommended to place such resistors in the customer design and not just assemble them. This
ensures that the module is compatible with other Apalis modules. There is no dedicated write-
protection signal available on the standard Apalis pin-out. Any free GPIO capable signal can be
used if the write-protection function is required.
2.13.2.1 SD Card Slot Reference Schematics
Both interfaces, the SD1 and the MMC1, can be used as SD Card slot interface. However, it is
recommended to use the MMC1 if only one card interface is used. According to the SD card
specifications, the host should be able to control the supply rail of the card. This allows the host to
cycle the supply rail of the card in order to do a full reset of the controller in the SD card. Most
cards do not require this procedure and work perfectly without a power switching feature. For
switching the card power rail, any free GPIO can be used. However, if the MMC1_D4 (pin 148) is
used, the latest Toradex BSP works without need for modifications.
Figure 42: 4bit SD Card Slot Reference Schematic
2.13.2.2 MMC Card Slot (8bit) Reference Schematics
Please note the different pin numbering of the MMC card in the following schematic. Even though
the selected 8-bit MMC card slot is compatible with SD cards, the pin numbering is different form
the normal SD cards.
To Next Page
Loading...
