ZYBO™ FPGA Board Reference Manual
Copyright Digilent, Inc. All rights reserved.
Other product and company names mentioned may be trademarks of their respective owners.
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Figure 5. USB-UART bridge.
Two on-board status LEDs provide visual feedback on traffic flowing through the port: the transmit LED (LD9) and
the receive LED (LD8). Signal names that imply direction are from the point-of-view of the DTE (Data Terminal
Equipment), in this case the PC.
The FT2232HQ is also used as the controller for the Digilent USB-JTAG circuitry, but the USB-UART and USB-JTAG
functions behave entirely independent of one another. Programmers interested in using the UART functionality of
the FT2232 within their design do not need to worry about the JTAG circuitry interfering with the UART data
transfers, and vice-versa. The combination of these two features into a single device allows the ZYBO to be
programmed, communicated with via UART, and powered from a computer attached with a single Micro USB
cable.
7
MicroSD Slot
The ZYBO provides a microSD slot (J4) for non-volatile external memory storage as well as booting the Zynq. The
slot is wired to Bank 1/501 MIO[40-47], including Card Detect. On the PS side peripheral SDIO 0 is mapped out to
these pins and controls communication with the SD card. The pinout can be seen in Table 4
Error! Reference
ource not found.
. The peripheral controller supports 1-bit and 4-bit SD transfer modes, but does not support SPI
mode. Based on the Zynq TRM, 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 4. MicroSD pinout.
The SD slot is a 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 2-port SDIO port expander, but only its level shifter
function is used. The connection diagram can be seen on Figure 6. Mapping out the correct pins and configuring
the interface is handled by the ZYBO board definition file.
