User manual

Zybo Z7 Board Reference Manual
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Page 18 of 31
peripheral SDIO 0 is mapped out to these pins and controls communication with the SD card. The pinout can be
seen in Table 8.1. The peripheral controller supports 1-bit and 4-bit SD transfer modes, but does not support SPI
mode. Based on the Zynq Technical Reference Manual, SDIO host mode is the only mode supported.
Signal Name
Description
Zynq Pin
SD Slot Pin
SD_D0
Data[0]
MIO42
7
SD_D1
Data[1]
MIO43
8
SD_D2
Data[2]
MIO44
1
SD_D3
Data[3]
MIO45
2
SD_CCLK
Clock
MIO40
5
SD_CMD
Command
MIO41
3
SD_CD
Card Detect
MIO47
9
Table 8.1. MicroSD pinout.
The SD slot is powered from 3.3V, but is connected through MIO Bank 1/501 (1.8V). Therefore, a TI TXS02612 level
shifter performs this translation. The TXS02612 is actually a 2-port SDIO port expander, but only its level shifter
function is used. The connection diagram can be seen on Figure 8.1. Mapping out the correct pins and configuring
the interface is handled by the Zybo Z7 board files, available on the Zybo Z7 resource center.
Figure 8.1. microSD slot signals.
Both low speed and high speed cards are supported, the maximum clock frequency being 50 MHz. A Class 4 card or
better is recommended.
Refer to section “2.1 microSD Boot Mode” for information on how to boot from a microSD card that contains a
Zynq Boot Image.
The microSD is also commonly used to store non-configuration data needed by the application. If doing this from a
bare-metal application, the microSD card can be freely accessed using standalone libraries included with a Xilinx
SDK BSP project. If doing this from a Petalinux generated embedded Linux system, the microSD can be
mounted/accessed like a standard block device, typically with a device node named /dev/mmcblk0. See the
Petalinux and Xilinx SDK documentation for more information.