Zybo Z7 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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USB Host/OTG
The Zybo Z7 implements one of the two available PS USB OTG interfaces on the Zynq device. A Microchip USB3320
USB 2.0 Transceiver Chip with an 8-bit ULPI interface is used as the PHY. The PHY features a complete HS-USB
Physical Front-End supporting speeds of up to 480Mbs. The PHY is connected to MIO Bank 1/501, which is
powered at 1.8V. The usb0 peripheral is used on the PS, connected through MIO[28-39]. The USB OTG interface
can act as an embedded host or a peripheral device. The USB mode is controlled from software by manipulating
the USB0 peripheral controller in the Zynq PS. When acting as a peripheral, the USB Micro AB connector (J10)
should be used to connect to a USB host device, and JP1 and JP2 should not be shorted. When acting as an
embedded host, the USB A connector (J11) should be used to connect to a USB peripheral device, and JP2 should
be shorted while JP1 is not shorted. The Zybo Z7 should never have a peripheral device and a host device
connected to these two connectors at the same time.
While in host mode, the Zybo Z7 is technic
ally an “embedded host”, because it does not provide the required 150
µF of capacitance on VBUS required to qualify as a general purpose host. It is possible to modify the Zybo Z7 so
that it complies with the general purpose USB host requirements by loading C71 with a 150 µF capacitor and
shorting JP1. Only those experienced at soldering small components on PCBs should attempt this rework. Most
USB peripheral devices will work just fine without loading C71. Whether the Zybo Z7 is configured as an embedded
host or a general purpose host, it can provide 500 mA on the 5V VBUS line. Note that loading C71 may cause the
Zybo Z7 to reset when booting embedded Linux while powered from the USB port, regardless of if any USB device
is connected to the host port. This is caused by the in-rush current that C71 causes when the USB host controller is
enabled and the VBUS power switch (IC12) is turned on.
Note that if your project uses the USB host feature (embedded or general purpose), then the Zybo Z7 is very likely
to consume more current than is allowed by a USB peripheral, causing it to periodically reset. When this occurs the
PGOOD LED will quickly flicker and the DONE LED will go low, indicating the PL is no longer programmed. To
prevent this, power the Zybo Z7 by a 5
V battery or wall adapter capable of providing more power. See section “1
Power Supplies” for information on acceptable non
-USB power sources.
10 Ethernet
The Zybo Z7 uses a Realtek RTL8211E-VL PHY to implement a 10/100/1000 Ethernet port for network connection.
The PHY connects to MIO Bank 501 (1.8V) and interfaces to the Zynq-7000 AP SoC via RGMII for data and MDIO for
management. The auxiliary interrupt (INTB) and reset (PHYRSTB) signals connect to PL pins to be accessed via
EMIO. The connection diagram can be seen on Figure 10.1.
After power-up the PHY starts with Auto Negotiation enabled, advertising 10/100/1000 link speeds and full duplex.
If there is an Ethernet-capable partner connected, the PHY automatically establishes a link with it, even with the
Zynq not configured.
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