Zybo Reference Manual

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ZYBO™ FPGA Board Reference Manual
Revised February 14, 2013
This manual applies to the ZYBO rev. B

Overview
The ZYBO (ZYnq BOard) is a feature-rich, ready-to-use, entry-level embedded software and digital circuit
development platform built around the smallest member of the Xilinx Zynq-7000 family, the Z-7010. The Z-7010 is
based on the Xilinx All Programmable System-on-Chip (AP SoC) architecture, which tightly integrates a dual-core
ARM Cortex-A9 processor with Xilinx 7-series Field Programmable Gate Array (FPGA) logic. When coupled with the
rich set of multimedia and connectivity peripherals available on the ZYBO, the Zynq Z-7010 can host a whole
system design. The on-board memories, video and audio I/O, dual-role USB, Ethernet, and SD slot will have your
design up-and-ready with no additional hardware needed. Additionally, six Pmod connectors are available to put
any design on an easy growth path.
The Zynq 7010 AP SoC offers the following features:






650Mhz dual-core Cortex-A9 processor
DDR3 memory controller with 8 DMA channels
High-bandwidth peripheral controllers: 1G Ethernet, USB 2.0, SDIO
2
Low-bandwidth peripheral controller: SPI, UART, CAN, I C
Reprogrammable logic equivalent to Artix-7 FPGA
o 4,400 logic slices, each with four 6-input LUTs and 8 flip-flops
o 240 KB of fast block RAM
o Two clock management tiles, each with a phase-locked loop (PLL) and mixed-mode clock
manager (MMCM)
o 80 DSP slices
o Internal clock speeds exceeding 450MHz
o On-chip analog-to-digital converter (XADC)

DOC#: 502-279

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ZYBO™ FPGA Board Reference Manual














The ZYBO Zynq-7000 development board.

ZYNQ XC7Z010-1CLG400C
512MB x32 DDR3 w/ 1050Mbps bandwidth
Dual-role (Source/Sink) HDMI port
16-bits per pixel VGA source port
Trimode (1Gbit/100Mbit/10Mbit) Ethernet PHY
MicroSD slot (supports Linux file system)
OTG USB 2.0 PHY (supports host and device)
External EEPROM (programmed with 48-bit
globally unique EUI-48/64™ compatible
identifier)
Audio codec with headphone out, microphone
and line in jacks
128Mb Serial Flash w/ QSPI interface
On-board JTAG programming and UART to USB
converter
GPIO: 6 pushbuttons, 4 slide switches, 5 LEDs
Six Pmod connectors (1 processor-dedicated, 1
dual analog/digital, 3 high-speed differential, 1
logic-dedicated)

The ZYBO is compatible with Xilinx's new high-performance Vivado Design Suite as well as the ISE/EDK toolset.
These toolsets meld FPGA logic design with embedded ARM software development into an easy to use, intuitive
design flow. They can be used for designing systems of any complexity, from a complete operating system running
multiple server applications in tandem, down to a simple bare-metal program that controls some LEDs.
An accessory kit that contains a 5V/2.5A power adapter, a USB A to Micro B cable, an 8GB speed class 10 microSD
card, and a Xilinx voucher for a Vivado Design Suite license will be available to purchase separately off of the
Digilent website in the near future. The Vivado Design Suite license enables use of the Logic Analyzer tools, which
accelerate debug and testing. This license is a 1 year, device-locked license, and will only work with the Z-7010
Zynq part on the ZYBO. After the license expires, any version of Vivado Design Suite that was released during this 1
year period can continue to be used indefinitely.

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Page 2 of 26

ZYBO™ FPGA Board Reference Manual
27

22
21
20

1
2

3
4

18
5

17
6

15
8
9

Callout

Component Description

Callout

Component Description

Power Switch

Processor Reset Pushbutton

Power Select Jumper and battery header

Logic configuration reset Pushbutton

Shared UART/JTAG USB port

Audio Codec Connectors

MIO LED

Logic Configuration Done LED

MIO Pushbuttons (2)

Board Power Good LED

MIO Pmod

JTAG Port for optional external cable

USB OTG Connectors

Programming Mode Jumper

Logic LEDs (4)

Independent JTAG Mode Enable Jumper

Logic Slide switches (4)

PLL Bypass Jumper

USB OTG Host/Device Select Jumpers

VGA connector

Standard Pmod

microSD connector (Reverse side)

High-speed Pmods (3)

HDMI Sink/Source Connector

Logic Pushbuttons (4)

Ethernet RJ45 Connector

XADC Pmod

Power Jack

Table 1. ZYBO Device Diagram.
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Page 3 of 26

ZYBO™ FPGA Board Reference Manual

Power Supplies

The ZYBO can be powered from the Digilent USB-JTAG-UART port (J11), or from an external power supply. Jumper
JP7 (near the power switch) determines which power source is used. There are three valid configurations for this
jumper corresponding to the three powering options: USB, wall wart with barrel jack, and battery pack. There is a
diagram on the board silkscreen indicating all three.
All on-board power supplies are enabled or disabled by the power switch SW4. The power indicator LED (LD11) is
on when all the supply rails reach their nominal voltage. An overview of the power circuit is shown in Fig.2

Power
Jack
(J15)

VU5V0

Power
Switch
(SW4)

JP7
J14

VIN

R281

PVIN5

1.5A

3.3V (III)

PVIN1-4

2.1A

1.0V (I)

1.2A
0.6A

1.5V (III)
1.8V (II)

0.1A

1.8V (III, analog)

D13

Micro-USB
Port (J11)

IC27: ADR127

Power-on Reset

PGOOD

IC26: ADP5052
Power Source Select

1.25V (III)

REF

Power On
LED (LD11)

JP7
J14
USB

WALL

BATTERY

VIN

0.1A

3.3V (IV, analog)

IC6: ADP150

Figure 2. Power circuit overview.

A USB 2.0 port can deliver maximum 0.5A of current according to the specifications. This should provide enough
power for lower complexity designs. An idling blank board consumes around 0.2A from the 5V input supply. As an
example, the standalone lwIP echo server sample project replying to ping requests consumes 0.38A on average.
More demanding applications, including any that drive multiple peripheral boards or other USB devices, might
require more power than the USB port can provide. In this case, power consumption will increase until it’s limited
by the USB host. This limit varies a lot between manufacturers and depends on many factors. When in current
limit, once the voltage rails dip below their nominal value, the Zynq is reset by the Power-on Reset signal and
power consumption returns to its idle value. Also, some applications may need to run without being connected to
a PC’s USB port. In these instances an external power supply or battery pack can be used.
An external power supply (wall wart) can be used by plugging into to the power jack (J15) and setting jumper JP7
to "wall". The supply must use a coax, center-positive 2.1mm internal-diameter plug, and deliver 4.5VDC to
5.5VDC and at least 2.5A of current (i.e., at least 12.5W of power). Suitable supplies can be purchased from the
Digilent website or through catalog vendors like DigiKey. Power supply voltages above 6VDC might cause
permanent damage.
An external battery pack can be used by connecting the battery’s positive terminal to the center pin of JP7 and the
negative terminal to the pin labeled J14 next to JP7. The external battery pack must be limited to 5.5VDC. The
minimum voltage of the battery pack depends on the application: if the USB Host (J10) or HDMI Source (J8)
function is used, at least 4.6V need to be provided. In other cases the minimum voltage is 3.6V.
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ZYBO™ FPGA Board Reference Manual
Voltage regulator circuits from Analog Devices create the required 3.3V, 1.8V, 1.5V, and 1.0V supplies from the main power input.
main power input.

Table 2 provides additional information (typical currents depend strongly on FPGA configuration and the values
provided are typical of medium size/speed designs).
Supply

Circuits

Device

Current (max/typical)

3.3V

FPGA I/O, USB ports, Clocks,
Ethernet, SD slot, Flash, HDMI

IC26#1: ADP5052

2.5A/0.1A to 1.5A

1.0V

FPGA, Ethernet Core

IC26#2: ADP5052

2.5A/0.2A to 2.1A

1.5V

DDR3

IC26#3: ADP5052

1.2A/0.1A to 1.2A

1.8V

FPGA Auxiliary, Ethernet I/O,
USB OTG

IC26#4: ADP5052

1.2A/0.1A to 0.6A

1.8V

XADC Analog

IC26#5: ADP5052

200mA/20mA

3.3V

Audio Analog

IC6: ADP150

150mA/50mA

1.25V

XADC Precision Reference

IC27: ADR127

5mA/50uA

Table 2. ZYBO power supplies.

The supply rails are daisy-chained to follow the Xilinx-recommended start-up sequence. Flicking the power switch
(SW4) will enable the 1.0V rail, which enables the 1.8V digital supply rail, which in turn enables the I/O supply rails
3.3V and 1.5V. The 1.25V reference and 1.8V analog supply ramp together with the 3.3V rail. Once all the channels
of the ADP5052 (IC26) supply reach regulation, the PGOOD signal will assert, enabling the 3.3V audio supply,
lighting up the power LED (LD11), and de-asserting the Power-On Reset signal (PS_POR_B) of the Zynq.
Each power supply uses a soft-start ramp of 1-10ms to limit in-rush current. There is an additional delay of at least
130ms after the power rails reach regulation and before the Power-On Reset signal de-assert to allow for the
PS_CLK (IC22) to stabilize.

Zynq AP SoC Architecture

The Zynq AP SoC is divided into two distinct subsystems: The Processing System (PS), and the Programmable Logic
(PL). Figure 3 shows an overview of the Zynq AP SoC architecture, with the PS colored light green and the PL in
yellow. Note that the PCIe Gen2 controller and Multi-gigabit transceivers are not available on the Zynq-7010
device.

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ZYBO™ FPGA Board Reference Manual

Figure 3. Zynq AP SoC architecture.

The PL is nearly identical to a Xilinx 7-series Artix FPGA, except that it contains several dedicated ports and buses
that tightly couple it to the PS. The PL also does not contain the same configuration hardware as a typical 7-series
FPGA, and it must be configured either directly by the processor or via the JTAG port.
The PS consists of many components, including the Application Processing Unit (APU, which includes 2 Cortex-A9
processors), Advanced Microcontroller Bus Architecture (AMBA) Interconnect, DDR3 Memory controller, and
various peripheral controllers with their inputs and outputs multiplexed to 54 dedicated pins (called
MultiplexedI/O, or MIO pins). Peripheral controllers that do not have their inputs and outputs connected to MIO
pins can instead route their I/O through the PL, via the Extended-MIO (EMIO) interface. The peripheral controllers
are connected to the processors as slaves via the AMBA interconnect, and contain readable/writable control
registers that are addressable in the processors’ memory space. The programmable logic is also connected to the
interconnect as a slave, and designs can implement multiple cores in the FPGA fabric that each also contain
addressable control registers. Furthermore, cores implemented in the PL can trigger interrupts to the processors
(connections not shown in Fig. 3) and perform DMA accesses to DDR3 memory.

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ZYBO™ FPGA Board Reference Manual
There are many aspects of the Zynq AP SoC architecture that are beyond the scope of this document. For a
complete and thorough description, refer to the Zynq Technical Reference Manual, available at www.xilinx.com.
Figure 3 depicts the external components connected to the MIO pins of the ZYBO. The Zynq Board Definition File
found on the Digilent ZYBO product page can be imported into EDK and Vivado Designs to properly configure the
PS to work with these peripherals.
MIO 500 3.3 V

Peripherals

Pmod

SPI Flash

GPIO

JF7

DQ0

DQ1

DQ2

DQ3

SCLK

LED4

SLCK FB

JF8

JF2

JF3

JF4

JF1

JF9

JF10

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ZYBO™ FPGA Board Reference Manual
MIO 501
1.8V
Pin

Peripherals
ENET 0

TXCK

TXD0

TXD1

TXD2

TXD3

TXCTL

RXCK

RXD0

RXD1

RXD2

RXD3

RXCTL

USB 0

DATA4

DIR

STP

NXT

DATA0

DATA1

DATA2

DATA3

CLK

DATA5

DATA6

DATA7

SDIO 0

CCLK

CMD

UART 1

GPIO

RESETN

RXD

TXD

BTN4

BTN5

MDC

MDIO
Table 3. MIO Pinout.

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ZYBO™ FPGA Board Reference Manual

Zynq Configuration

Unlike Xilinx FPGA devices, AP SoC devices such as the Zynq-7010 are designed around the processor, which acts as
a master to the programmable logic fabric and all other on-chip peripherals in the processing system. This causes
the Zynq boot process to be more similar to that of a microcontroller than an FPGA. This process involves the
processor loading and executing a Zynq Boot Image, which includes a First Stage Bootloader (FSBL), a bitstream for
configuring the programmable logic (optional), and a user application.
The boot process is broken into three stages:
Stage 0
After the ZYBO is powered on or the Zynq is reset (in software or by pressing PS-SRST), one of the
processors (CPU0) begins executing an internal piece of read-only code called the BootROM. If and only if
the Zynq was just powered on, the BootROM will first latch the state of the mode pins into the mode
register (the mode pins are attached to JP5 on the ZYBO). If the BootROM is being executed due to a reset
event, then the mode pins are not latched, and the previous state of the mode register is used. This
means that the ZYBO needs a power cycle to register any change in the programming mode jumper (JP5).
Next, the BootROM copies an FSBL from the form of non-volatile memory specified by the mode register
to the 256 KB of internal RAM within the APU (called On-Chip Memory, or OCM). The FSBL must be
wrapped up in a Zynq Boot Image in order for the BootROM to properly copy it. The last thing the
BootROM does is hand off execution to the FSBL in OCM.
Stage 1
During this stage, the FSBL first finishes configuring the PS components, such as the DDR memory
controller. Then, if a bitstream is present in the Zynq Boot Image, it is read and used to configure the PL.
Finally, the user application is loaded into memory from the Zynq Boot Image, and execution is handed off
to it.
Stage 2
The last stage is the execution of the user application that was loaded by the FSBL. This can be any sort of
program, from a simple “Hello World” design, to a Second Stage Boot loader used to boot an operating
system like Linux. For a more thorough explanation of the boot process, refer to Chapter 6 of the Zynq
Technical Reference Manual.
The Zynq Boot Image is created using Vivado and Xilinx Software Development Kit (Xilinx SDK). For a tutorial on
how to build an image using these tools that properly targets the ZYBO, download the ZYBO Base System Design
from the Digilent ZYBO product page and follow the included documentation.
The ZYBO supports three different boot modes: microSD, QSPI Flash, and JTAG. The boot mode is selected using
the Mode jumper (JP5), which affects the state of the Zynq configuration pins after power-on. Figure 4 depicts how
the Zynq configuration pins are connected on the ZYBO. Note that MIO2-MIO8 are shared with the QSPI Flash and
MIO LED, but not pictured in Fig. 4.

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Page 9 of 26

ZYBO™ FPGA Board Reference Manual
USB-JTAG/UART Port
Micro-AB USB
Connector (J11)

6-pin JTAG
Header (J12)

Zynq

USB
Controller

1x6 JTAG
Header

JP6

MIO2/M3
JTAG
Port

Mode (JP5)

MIO3/M1
MIO4/M2
MIO5/M0
MIO6/M4

MIO7/VCFG0

JP4
JP5

MIO8/VCFG1

MicroSD

PROGRAM_B
DONE
PS_SRST_B

QSPI Flash
JTAG

Programming Mode

Figure 4. ZYBO configuration pins.

The three boot modes are described in the following sections.

3.1

MicroSD Boot Mode

The ZYBO supports booting from a microSD card inserted into connector J4. The following procedure will allow you
to boot the Zynq from microSD:
1)
2)
3)
4)
5)
6)
7)

3.2

Format the microSD card with a FAT32 file system.
Copy the Zynq Boot Image created with Xilinx SDK to the microSD card.
Rename the Zynq Boot Image on the microSD card to BOOT.bin.
Eject the microSD card from your computer and insert it into connector J4 on the ZYBO.
Attach a power source to the ZYBO and select it using JP7.
Place a single jumper on JP5, shorting the two leftmost pins (labeled “SD”).
Turn the board on. The board will now boot the image on the microSD card.

QSPI Boot Mode

The ZYBO has an onboard 128-Mbit Quad-SPI (QSPI) serial Flash that the Zynq can boot from. The ZYBO Base
System Design includes a tutorial for how to configure the QSPI Flash with a Zynq Boot Image using the iMPACT
tool included with Xilinx ISE and Vivado. Once the QSPI Flash has been loaded with a Zynq Boot Image, the
following steps can be followed to boot from it:
1) Attach a power source to the ZYBO and select it using JP7.
2) Place a single jumper on JP5, shorting the two center pins (labeled “QSPI”).
3) Turn the board on. The board will now boot the image stored in the QSPI flash.
The ZYBO ships with a demonstration application pre-loaded into QSPI. For information on this image and how to
restore it if erased, download the Factory Loaded Demo project from the ZYBO page at www.digilentinc.com.

3.3

JTAG Boot Mode

When placed in JTAG boot mode, the processor will wait until software is loaded by a host computer using the
Xilinx tools. After software has been loaded, it is possible to either let the software begin executing, or step

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Page 10 of 26

ZYBO™ FPGA Board Reference Manual
through it line by line using Xilinx SDK. The ZYBO Base System Design includes a tutorial for debugging software
over JTAG in Xilinx SDK.
It is also possible to directly configure the PL over JTAG, independent of the processor. This can be done using
iMPACT or the Vivado Hardware Server.
The ZYBO is configured to boot in Cascaded JTAG mode, which allows the PS to be accessed via the same JTAG port
as the PL. It is also possible to boot the ZYBO in Independent JTAG mode by loading a jumper in JP6 and shorting it.
This will cause the PS to not be accessible from the onboard JTAG circuitry, and only the PL will be visible in the
scan chain. To access the PS over JTAG while in independent JTAG mode, users will have to route the signals for the
PJTAG peripheral over EMIO, and use an external device to communicate with it.

SPI Flash

The ZYBO features a 4-bit SPI (quad-SPI) serial NOR flash. The Spansion S25FL128S is used on this board. The MultiI/O SPI Flash memory is used to provide non-volatile code and data storage. It can be used to initialize the PS
subsystem as well as configure the PL subsystem (bitstream). Spansion provides Spansion Flash File System (FFS)
for use after booting the Zynq-7000 AP SoC.
The relevant device attributes are:





128Mbit
x1, x2, and x4 support
Speeds up to 104 MHz, supporting Zynq configuration rates @ 100 MHz. In Quad-SPI mode, this
translates to 400Mbs
Powered from 3.3V

The SPI Flash connects to the Zynq-7000 AP SoC supporting up to Quad-I/O SPI interface. This requires connection
to specific pins in MIO Bank 0/500, specifically MIO[1:6,8] as outlined in the Zynq datasheet. Quad-SPI feedback
mode is used, thus qspi_sclk_fb_out/MIO[8] is left to freely toggle and is connected only to a 20K pull-up resistor
to 3.3V. This allows a QSPI clock frequency greater than FQSPICLK2.

DDR Memory

The ZYBO includes two Micron MT41J128M16JT-125 or MT41K128M16JT-125 DDR3 memory components creating
a single rank, 32-bit wide interface and a total of 512MiB of capacity. The DDR3 is connected to the hard memory
controller in the Processor Subsystem (PS), as outlined in the Zynq documentation. The PS incorporates an AXI
memory port interface, a DDR controller, the associated PHY, and a dedicated I/O bank. DDR3 memory interface
1
speeds up to 533 MHz/1066 Mbps are supported .
The DDR3 uses 1.5V SSTL-compatible inputs. The two components are organized in a tree topology with a series
termination scheme while keeping traces as short as possible and matched.
ZYBO was routed with 40 ohm (+/-10%) trace impedance for single-ended signals, and differential clock and
strobes set to 80 ohms (+/-10%). A feature called DCI (Digitally Controlled Impedance) is used to match the drive

Maximum actual clock frequency is 525 MHz due to PLL limitation.

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Page 11 of 26

ZYBO™ FPGA Board Reference Manual
strength and termination impedance of the PS pins to the trace impedance. On the memory side, each chip
calibrates its on-die termination and drive strength using a 240 ohm resistor on the ZQ pin.
Due to layout reasons, the two lower data byte groups (DQ[0-7], DQ[8-15]) were swapped. To the same effect, the
data bits inside byte groups were swapped as well. These changes are transparent to the user. During the whole
design process the Xilinx PCB guidelines were followed.
Both the memory chips and the PS DDR bank are powered from the 1.5V supply. The mid-point reference of 0.75V
is created with a simple resistor divider and is available to the Zynq as external reference.
For proper operation it is essential that the PS memory controller is configured properly. Settings range from the
actual memory flavor to the board trace delays. For your convenience the board definition file provided on our
website will automatically configure the correct parameters.
For best DDR3 performance, DRAM training is enabled for write leveling, read gate, and read data eye options in
the PS Configuration Tool in Xilinx tools. Training is done dynamically by the controller to account for board delays,
process variations and thermal drift. Optimum starting values for the training process are the board delays
(propagation delays) for certain memory signals.
Board delays are specified for each of the byte groups. These parameters are board-specific and were calculated
from the PCB trace length reports. The DQS to CLK Delay and Board Delay values are calculated specific to the
ZYBO memory interface PCB design.
For more details on memory controller operation, refer to the Xilinx Zynq TRM (ug585).

USB UART Bridge (Serial Port)

The ZYBO includes an FTDI FT2232HQ USB-UART bridge (attached to connector J11) that lets you use PC
applications to communicate with the board using standard Windows COM port commands. Free USB-COM port
drivers, available from www.ftdichip.com under the "Virtual Com Port" or VCP heading, convert USB packets to
UART/serial port data. Serial port data is exchanged with the Zynq using a two-wire serial port (TXD/RXD). After the
drivers are installed, I/O commands can be used from the PC directed to the COM port to produce serial data
traffic on the Zynq pins. The port is tied to PS (MIO) pins and can be used in combination with the UART 1
controller. A 3.3V->1.8V voltage level translation interfaces the FT2232 with MIO Bank 501, a process transparent
to the user.
The board definition file takes care of mapping the correct MIO pins to the UART 1 controller and uses the
following default protocol parameters: 115200 baud rate, 1 stop bit, no parity, 8-bit character length.

2
Micro-USB
(J11)

4
JTAG

JTAG

TXD
RXD

MIO48
MIO49

Zynq-7
TX LED
RX LED

LD9
LD8

FT2232

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Page 12 of 26

ZYBO™ FPGA Board Reference Manual
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.

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 4Error! 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

SD_D1

Data[1]

MIO43

SD_D2

Data[2]

MIO44

SD_D3

Data[3]

MIO45

SD_CCLK

Clock

MIO40

SD_CMD

Command

MIO41

SD_CD

Card Detect

MIO47

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.

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ZYBO™ FPGA Board Reference Manual
1.8V

DAT2
DAT3
CMD
VDD
CLK
GND
DAT0
DAT1

SD MICRO

3.3V

SD_D2
SD_D3
SD_CMD

MIO47
MIO44
MIO45
MIO41

SD_CCLK

MIO40

SD_D0
SD_D1

MIO42
MIO43

TXS02612RTWR

Zynq-7

Voltage Level Translator

Figure 6. 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 3.1 for information on how to boot from an SD card. For more information, consult the Xilinx Zynq
TRM (ug585).

USB OTG

The ZYBO 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. When acting as a peripheral, the USB Micro AB connector (J9) should
be used to connect to a USB host device, and JP1 should not be shorted. When acting as an embedded host, the
USB A connector (J10) should be used to connect to a USB peripheral device, and JP1 should be shorted. The ZYBO
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 is technically 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 so that it
complies with the general purpose USB host requirements by loading C64 with a 150 µF capacitor and shorting JP2.
Only those experienced at soldering small components on PCBs should attempt this rework. Many USB peripheral
devices will work just fine without loading C64. Whether the ZYBO is configured as an embedded host or a general
purpose host, it can provide 500 mA on the 5V VBUS line.
Note that if your design uses the USB OTG feature in host mode (embedded or general purpose), then the ZYBO
should not be powered via USB (J11), but instead by a battery or wall adapter capable of providing more power.

Ethernet PHY

The ZYBO 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 Fig. 7.
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ZYBO™ FPGA Board Reference Manual
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.

MIO53
MIO52

MDIO
MDC

MIO23
MIO24
MIO25
MIO26
MIO27
MIO22

RXD0/SELRGV
RXD1/TXDLY
RXD2/AN0
RXD3/AN1
RXCTL/PHY_AD2
RXC

MIO17
MIO18
MIO19
MIO20
MIO21
MIO16

TXD0
TXD1
TXD2
TXD3
TXCTL
TXC

F16
E17
L16

RJ-45 with
magnetics
8

INTB
PHYRSTB
CLK125
LED0/PHY_AD0

PS_CLK

Zynq-7

CKXTAL1

50 MHz
Oscillator
DSC1121CE5

ACT LED (LD7)
LINK LED (LD6)

LED1/PHY_AD1

Realtek RTL8211E

Figure 7. Ethernet PHY signals.

Two status indicator LEDs are on-board near the RJ-45 connector that indicate traffic (LD7) and valid link state
(LD6). Table 5 shows the default behavior.
Function

Designator

LINK

LD6

ACT

LD7

State

Description

Link 10/100/1000

Blinking 0.4s ON, 2s OFF

Link, Energy Efficient Ethernet (EEE) mode

Blinking

Transmitting or Receiving
Table 5. Ethernet status LEDs.

The Zynq incorporates two independent Gigabit Ethernet Controllers. They implement a 10/100/1000 half/full
duplex Ethernet MAC. Of these two, GEM 0 can be mapped to the MIO pins where the PHY interfaces. Since the
MIO bank is powered from 1.8V, the RGMII interface uses 1.8V HSTL Class 1 drivers. For this I/O standard an
external reference of 0.9V is provided in bank 501 (PS_MIO_VREF). Mapping out the correct pins and configuring
the interface is handled by the ZYBO board definition file.

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ZYBO™ FPGA Board Reference Manual
Although the default power-up configuration of the PHY might be enough in most applications, the MDIO bus is
available for management. The RTL8211E-VL is assigned address 00001b. With simple register read and write
commands, status information can be read out or configuration changed. The Realtek PHY follows industrystandard register map for basic configuration.
The RGMII specification calls for the receive (RXC) and transmit clock (TXC) to be delayed relative to the data
signals (RXD[0:3], RXCTL and TXD[0:3], TXCTL). Xilinx PCB guidelines also require this delay to be added. The
RTL8211E-VL is capable of inserting a 2ns delay on both the TXC and RXC so that board traces do not need to be
made longer.
The PHY is clocked from the same 50 MHz oscillator (IC22) that clocks the PS too. The parasitic capacitance of the
two loads is low enough to be driven from a single source.
On an Ethernet network each node needs a unique MAC address. To this end, a Microchip 24AA02E48 EEPROM is
2
provided on the ZYBO. On one hand it is a read-writeable EEPROM that can be accessed via I C. On the other hand
it features a read-only memory section that comes pre-programmed with a unique identifier. This unique identifier
2
can be read and used as a MAC address, avoiding a possible address conflict on the network. The I C interface
connects to the PL side and can be accessed from the PS over EMIO as well. The device address of the EEPROM is
1010000b.
For more information on using the Gigabit Ethernet MAC, refer to the Xilinx Zynq TRM (ug585).

HDMI Source/Sink Port

An input and output-capable HDMI Port connects to the programmable logic pins. Over this connector an HDMI or
DVI-compatible video stream can be driven in or out of the ZYBO. Encoding or decoding the HDMI/DVI video
stream needs to be implemented in logic, as well as auxiliary functions, like DDC or CEC. Depending on the actual
design, it can take the Source role driving a monitor/TV display, or behave as a Sink accepting a video stream from
any HDMI/DVI Source, like a laptop or smartphone.
On-board auxiliary buffers and electronic switches control the direction of signals that differ between Source and
Sink. These signals are summarized Table 6.
Signal
HPD
5V0

Role

Description

Direction (Zynq POW)

How to control

Source

Hot-plug detect; signals the
presence of a Sink to a Source

Input

HDMI_OUT_EN = 1

Output

HDMI_OUT_EN = 0

Output
Input

HDMI_OUT_EN = 1
HDMI_OUT_EN = 0

Sink
Source
Sink

Auxiliary power for Sink

Table 6. HDMI signal direction in Source and Sink roles.

The CEC function is bi-directional by definition, so it is treated the same no matter what role the port takes. If the
CEC function is not used, declare it as input and constrain it to the correct PL pin to leave other devices on the CEC
bus unaffected.
When operating as Sink, the DDC function is required to be implemented so that a connected Source can read out
2
important characteristics of the device. This can be done by emulating an I C-capable EEPROM in programmable
logic. Likewise, in Source mode DDC can be used to find out the capabilities of the connected display.

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Page 16 of 26

ZYBO™ FPGA Board Reference Manual
The HDMI/DVI protocol uses TMDS (Transition-minimized differential signaling) as I/O standard. It is supported on
Zynq by the I/O buffers on the programmable logic side. 50 ohm external parallel termination resistors are
provided on-board. HDMI specifications only require terminations on the Sink side, but optional Source-side
terminations reduce reflections, resulting in improved signal quality. Do not connect powered HDMI/DVI devices to
an unpowered ZYBO, as it might result in back-powering the board through the termination resistors.
Resolutions up to 720p (1280x720) have been tested.
HDMI and DVI are high-speed source-synchronous serial protocols. Implementations on FPGA are required to use
certain built-in primitives to properly synthesize the correct clock frequency, serialize the transmission, and keep a
lock on the signal. The actual implementation of the HDMI/DVI protocols is outside the scope of this manual.
Check for upcoming reference projects on our website or consult relevant specifications and Xilinx documentation.

VGA Port

The ZYBO board uses 18 programmable logic pins to create an
analog VGA output port. This translates to 16-bit color depth and
two standard sync signals (HS – Horizontal Sync, and VS – Vertical
Sync).
The digital-to-analog conversion is done using a simple R-2R
2
resistor ladder . The ladder works in conjunction with the 75-ohm
termination resistance of the VGA display to create 32 and 64
analog signal levels red, blue, and green VGA signals. This circuit,
shown in Fig. 8, produces video color signals that proceed in equal
increments between 0V (fully off) and 0.7V (fully on). With 5 bits
each for red and blue and 6 bits for green, 65,536 (32×32×64)
different colors can be displayed, one for each unique 16-bit
pattern.
A video controller circuit must be created in programmable logic
to drive the sync and color signals with the correct timing in order
to produce a working display system.

Pin 1: Red
Pin 2: Grn
Pin 3: Blue
Pin 13: HS
Pin 14: VS

Pin 5: GND
Pin 6: Red GND
Pin 7: Grn GND
Pin 8: Blu GND
Pin 10: Sync GND

F19

RED5

536W

G20

RED4

536W

270W

536W

270W

J20

RED3
RED2

270W

L20

536W
536W

270W

M19

RED1

536W

RED

BLU

HD-DB15F

F20

GRN5

536W

GRN4

536W

270W

H20
J19

GRN3

536W

270W

L19

GRN2

536W

270W

N20

GRN1

536W

270W

GRN0

536W

270W

H18

GRN

536W

G19

BLU5

536W

BLU4

536W

270W

J18

BLU3

536W

270W

K19
M20

BLU2

536W

270W

P20

BLU1

536W

270W
536W

P19
R19

HSYNC 100W
VSYNC

100W

Zynq- 7
Figure 8. ZYBO VGA circuit.

http://en.wikipedia.org/wiki/Resistor_ladder

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Page 17 of 26

ZYBO™ FPGA Board Reference Manual

11.1 VGA System Timing
VGA signal timings are specified, published, copyrighted, and sold by the VESA organization (www.vesa.org). The
following VGA system timing information is provided as an example of how a VGA monitor might be driven in 640
by 480 mode.
NOTE: For more precise information, or for information on other VGA frequencies, refer to documentation
available at the VESA website.
CRT-based VGA displays use amplitude-modulated moving electron beams (or cathode rays) to display information
on a phosphor-coated screen. LCD displays use an array of switches that can impose a voltage across a small
amount of liquid crystal, thereby changing light permittivity through the crystal on a pixel-by-pixel basis. Although
the following description is limited to CRT displays, LCD displays have evolved to use the same signal timings as
CRT displays (so the “signals” discussion below pertains to both CRTs and LCDs). Color CRT displays use three
electron beams (one for red, one for blue, and one for green) to energize the phosphor that coats the inner side of
the display end of a cathode ray tube (see Fig. 9).

Anode (entire screen)
Cathode ray tube
Deflection coils
Grid

Electron guns
(Red, Blue, Green)

Cathode ray

R,G,B signals
(to guns)

VGA
cable
High voltage deflection grid
supply (>20kV) control control

gun
control

Figure 9. Color CRT display.

Electron beams emanate from “electron guns” which are finely-pointed heated cathodes placed in close proximity
to a positively charged annular plate called a “grid.” The electrostatic force imposed by the grid pulls rays of
energized electrons from the cathodes, and those rays are fed by the current that flows into the cathodes. These
particle rays are initially accelerated towards the grid, but they soon fall under the influence of the much larger
electrostatic force that results from the entire phosphor-coated display surface of the CRT being charged to 20kV
(or more). The rays are focused to a fine beam as they pass through the center of the grids, and then they
accelerate to impact on the phosphor-coated display surface. The phosphor surface glows brightly at the impact
point, and it continues to glow for several hundred microseconds after the beam is removed. The larger the
current fed into the cathode, the brighter the phosphor will glow.
Between the grid and the display surface, the beam passes through the neck of the CRT where two coils of wire
produce orthogonal electromagnetic fields. Because cathode rays are composed of charged particles (electrons),
they can be deflected by these magnetic fields. Current waveforms are passed through the coils to produce
magnetic fields that interact with the cathode rays and cause them to transverse the display surface in a “raster”
pattern, horizontally from left to right and vertically from top to bottom, as shown in Fig. 10. As the cathode ray

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Page 18 of 26

ZYBO™ FPGA Board Reference Manual
moves over the surface of the display, the current sent to the electron guns can be increased or decreased to
change the brightness of the display at the cathode ray impact point.
Information is only displayed when the beam is moving in the “forward” direction (left to right and top to bottom),
and not during the time the beam is reset back to the left or top edge of the display. Much of the potential display
time is therefore lost in “blanking” periods when the beam is reset and stabilized to begin a new horizontal or
vertical display pass. The size of the beams, the frequency at which the beam can be traced across the display, and
the frequency at which the electron beam can be modulated determine the display resolution.
Modern VGA displays can accommodate different resolutions, and a VGA controller circuit dictates the resolution
by producing timing signals to control the raster patterns. The controller must produce synchronizing pulses at
3.3V (or 5V) to set the frequency at which current flows through the deflection coils, and it must ensure that video
data is applied to the electron guns at the correct time. Raster video displays define a number of “rows” that
corresponds to the number of horizontal passes the cathode makes over the display area, and a number of
“columns” that corresponds to an area on each row that is assigned to one “picture element”, or pixel. Typical
displays use from 240 to 1200 rows and from 320 to 1600 columns. The overall size of a display and the number of
rows and columns determines the size of each pixel.

pixel 0,0

pixel 0,639

640 pixels per row are displayed
during forward beam trace

Display Surface

pixel 479,0

Retrace - no
information
displayed
during this
time

pixel 479,639

Stable current ramp - information
is displayed during this time
Current
waveform
through
horizontal
defletion
coil

Total horizontal time
Horizontal display time

retrace
time

time

HS
"front porch"

Horizontal sync signal
sets retrace frequency

"back porch"

Figure 10. VGA horizontal synchronization.

Video data typically comes from a video refresh memory; with one or more bytes assigned to each pixel location
(the ZYBO uses 16 bits per pixel). The controller must index into video memory as the beams move across the
display, and retrieve and apply video data to the display at precisely the time the electron beam is moving across a
given pixel.
A VGA controller circuit must generate the HS and VS timings signals and coordinate the delivery of video data
based on the pixel clock. The pixel clock defines the time available to display one pixel of information. The VS signal
defines the “refresh” frequency of the display, or the frequency at which all information on the display is redrawn.
The minimum refresh frequency is a function of the display’s phosphor and electron beam intensity, with practical
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Page 19 of 26

ZYBO™ FPGA Board Reference Manual
refresh frequencies falling in the 50Hz to 120Hz range. The number of lines to be displayed at a given refresh
frequency defines the horizontal “retrace” frequency. For a 640-pixel by 480-row display using a 25MHz pixel clock
and 60 +/-1Hz refresh, the signal timings shown in Fig. 11 can be derived. Timings for sync pulse width and front
and back porch intervals (porch intervals are the pre- and post-sync pulse times during which information cannot
be displayed) are based on observations taken from actual VGA displays.
TS
Tfp

Tdisp

T pw

Symbol Parameter
TS

Sync pulse

T disp Display time

Tbp

Horiz. Sync
Vertical Sync
Time Clocks Lines Time Clks
16.7ms 416,800

521

32 us

800

15.36ms 384,000

480

25.6 us

640

T pw

Pulse width

64 us

1,600

3.84 us

T fp

Front porch

320 us

8,000

640 ns

T bp

Back porch

928 us

23,200

1.92 us

Figure 11. Signal timings for a 640-pixel by 480 row display using a 25MHz pixel clock and 60Hz vertical refresh.

A VGA controller circuit, such as the one diagramed in Fig. 12, decodes the output of a horizontal-sync counter
driven by the pixel clock to generate HS signal timings. You can use this counter to locate any pixel location on a
given row. Likewise, the output of a vertical-sync counter that increments with each HS pulse can be used to
generate VS signal timings, and you can use this counter to locate any given row. These two continually running
counters can be used to form an address into video RAM. No time relationship between the onset of the HS pulse
and the onset of the VS pulse is specified, so you can arrange the counters to easily form video RAM addresses, or
to minimize decoding logic for sync pulse generation.

Pixel
CLK

Horizontal
Counter

Zero
Detect

Set

3.84us
Detect

Reset

Horizontal
Synch

CE
Vertical
Counter

Zero
Detect

Set
Vertical
Synch

64us
Detect

Reset

Figure 12. VGA display controller block diagram.

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ZYBO™ FPGA Board Reference Manual

Clock Sources

The ZYBO provides a 50 MHz clock to the Zynq PS_CLK input, which is used to generate the clocks for each of the
PS subsystems. The 50 MHz input allows the processor to operate at a maximum frequency of 650 MHz and the
DDR3 memory controller to operate at a maximum of 525 MHz (1050 Mbps). The ZYBO Base System Design
configures the PS to work properly with this input clock, and should be used as a reference when creating custom
designs.
The PS has a dedicated PLL capable of generating up to four reference clocks, each with settable frequencies, that
can be used to clock custom logic implemented in the PL. Additionally, The ZYBO provides an external 125 MHz
reference clock directly to pin L16 of the PL. The external reference clock allows the PL to be used completely
independently of the PS, which can be useful for simple applications that do not require the processor.
The PL of the Zynq-Z7010 also includes two MMCM’s and two PLL’s that can be used to generate clocks with
precise frequencies and phase relationships. Any of the four PS reference clocks or the 125 MHz external reference
clock can be used as an input to the MMCMs and PLLs. For a full description of the capabilities of the Zynq PL
clocking resources, refer to the “7 Series FPGAs Clocking Resources User Guide” available from Xilinx.
Figure 13 outlines the clocking scheme used on the ZYBO. Note that the reference clock output from the Ethernet
PHY is used as the 125 MHz reference clock to the PL, in order to cut the cost of including a dedicated oscillator for
this purpose. Keep in mind that CLK125 will be disabled when the Ethernet PHY (IC1) is held in hardware reset by
driving the PHYRSTB signal low.
50 MHz Oscillator
(IC22)
OUT

3.3V

PS_CLK

CKXTAL1
CLK125
PHYRSTB

Ethernet PHY (IC1)

PS
PLL

FCLK_CLK[0:3]
L16

PL
E17

Zynq

Figure 13. ZYBO clocking.

Basic I/O

The ZYBO board includes four slide switches, four push buttons, and four individual LEDs connected to the Zynq PL,
as shown in Fig. 14. There are also two additional pushbuttons and one LED connected directly to the PS via MIO
pins, also shown in Fig. 14. The pushbuttons and slide switches are connected to the Zynq via series resistors to
prevent damage from inadvertent short circuits (a short circuit could occur if a pin assigned to a pushbutton or
slide switch was inadvertently defined as an output). The pushbuttons are "momentary" switches that normally
generate a low output when they are at rest, and a high output only when they are pressed. Slide switches
generate constant high or low inputs depending on their position.

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3.3V
MIO
Buttons

MIO51

BTN5

MIO7

MIO
LED
LD12

MIO50

BTN4
3.3V

Buttons

Y16

BTN3

V16

BTN2

P16

BTN1

LEDs

R18

BTN0

D18
G14
M15
M14

3.3V

Slide
Switches

SW3

T16

SW2

W13

SW1

P15

SW0

G15

LD3
LD2
LD1
LD0

Zynq

Figure 14. ZYBO GPIO.

The high-efficiency LEDs are anode-connected to the Zynq via 330-ohm resistors, so they will turn on when a logic
high voltage is applied to their respective I/O pin. Additional LEDs that are not user-accessible indicate power-on,
FPGA programming status, and USB and Ethernet port status.
The LED and two pushbuttons attached directly to the PS are accessed using the Zynq GPIO controller. This core is
described in full in Chapter 14 of the Zynq Technical Reference Manual.

Audio

An Analog Devices SSM2603 Audio Codec provides integrated digital audio processing to the Zynq-7000 AP SoC. It
allows for stereo record and playback at sample rates from 8 kHz to 96 kHz.
On the analog side, the codec connects to three 3.5 mm standard audio jacks. There are two inputs: a mono
microphone and a stereo line in. There is one stereo output, the headphone jack. Analog power is provided by a
dedicated linear power supply (IC6).
Audio Jack

Description

Channels

Color

SSM2603 pin

Headphone Out

Stereo

Black

L/RHPOUT

Microphone In

Mono

Pink

MICIN, MICBIAS

Line In

Stereo

Light Blue

L/RLINEIN

Table 7. Analog audio signals.

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ZYBO™ FPGA Board Reference Manual
The digital interface of the SSM2603 is wired to the programmable logic side of the Zynq. Audio data is transferred
2
2
via the I S protocol. Configuration is done over an I C bus. The device address of the SSM2603 is 0011010b. All
digital I/O are 3.3V level and connect to a 3.3V-powered FPGA bank.
SSM2603 pin

Protocol

BCLK

Direction (Zynq POW)

Zynq pin

Output

K18

Output

M17

Output

L17

Input

K17

Output

M18

Input/Output

N17

I S (Serial Clock)

PBDAT

I S (Playback Data)

PBLRC

I S (Playback Channel Clock)

RECDAT

I S (Record Data)

RECLRC

I S (Record Channel Clock)

SDIN

I C (Data)

SCLK

I C (Clock)

Output

N18

MUTE

Digital Enable (Active Low)

Output

P18

MCLK

Master Clock

Output

T19

Table 8. Digital audio signals, with the SSM2603 in default slave mode.

The audio codec needs to be clocked from the Zynq on the MCLK pin. This master clock will be used by the audio
codec to establish the audio sampling frequency. This clock is required to be an integer multiple of the desired
sampling rate. The default settings require a master clock of 12.288 Mhz, resulting in a 48 kHz sampling rate. For
other frequencies and their respective configuration parameters, consult the SSM2603 datasheet.
The codec has two modes: master and slave, with the slave being default. In this mode, the direction of the signals
is specified in Table 8. When configured as master, the direction of BCLK, PBLRC and RECLRC is inverted. In this
mode, the codec generates the proper frequencies for these clocks. No matter where are the clocks are generated,
PBDAT needs to be driven out and RECDAT sampled in sync with them. The master clock is always driven out of the
2
Zynq. The timing diagram of an I S stream can be seen on Figure 15. Note the one-cycle delay of the data stream
with respect to the left/right clock changing state. Audio samples are transmitted MSB first, noted as 1 in the
diagram.
1/fs
BCLK

PB/RECLRC

PB/RECDAT

Figure 15. I2S timing diagram.

The digital mute signal (MUTE) is active-low, with a pull-down resistor. This means that when not used in the
design, it will stay low and the analog outputs of the codec will stay muted. To enable the analog outputs, drive
this signal high.
2

To use the audio codec in a design with non-default settings, it needs to be configured over I C. The audio path
needs to be established by configuring the (de)multiplexers and amplifiers in the codec. Some digital processing
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Page 23 of 26

ZYBO™ FPGA Board Reference Manual
2

can also be done in the codec. Configuration is read out and written by accessing the register map via I C transfers.
The register map is described in the SSM2603 datasheet.

Reset Sources

15.1 Power-on Reset
The Zynq PS supports external power-on reset signals. The power-on reset is the master reset of the entire chip.
This signal resets every register in the device capable of being reset. The ZYBO drives this signal from a comparator
that holds the system in reset until all power supplies are valid. Several other IC’s on the ZYBO are reset by this
signal as well.

15.2 Program Push-button Switch
A PROG push switch, BTN6, toggles Zynq PROG_B. This resets the PL and causes DONE to be de-asserted. The PL
will remain unconfigured until it is reprogrammed by the processor or via JTAG.

15.3 Processor Subsystem Reset
The external system reset, labeled PS_SRST/BTN7, resets the Zynq device without disturbing the debug
environment. For example, the previous break points set by the user remain valid after system reset. Due to
security concerns, system reset erases all memory content within the PS, including the OCM. The PL is also cleared
during a system reset. System reset does not cause the boot mode strapping pins to be re-sampled.

Pmod Connectors

Pmod connectors are 2x6, right-angle, 100-mil spaced female connectors that mate with standard 2x6 pin headers.
Each 12-pin Pmod connector provides two 3.3V VCC signals (pins 6 and 12), two Ground signals (pins 5 and 11),
and eight logic signals, as shown in Fig. 16. The VCC and Ground pins can deliver up to 1A of current, but care must
be taken not to exceed any of the power budgets of the onboard regulators or the external power supply.

VCC GND

8 signals
Pin 1

Pin 6

Pin 12

Figure 16. Pmod diagram.

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ZYBO™ FPGA Board Reference Manual
Pmod JA
(XADC)

Pmod JB
(Hi-Speed)

Pmod JC
(Hi-Speed)

Pmod JD
(Hi-Speed)

Pmod JE
(Std.)

Pmod JF
(MIO)

JA1: N15

JB1: T20

JC1: V15

JD1: T14

JE1: V12

JF1: MIO-13

JA2: L14

JB2: U20

JC2: W15

JD2: T15

JE2: W16

JF2: MIO-10

JA3: K16

JB3: V20

JC3: T11

JD3: P14

JE3: J15

JF3: MIO-11

JA4: K14

JB4: W20

JC4: T10

JD4: R14

JE4: H15

JF4: MIO-12

JA7: N16

JB7: Y18

JC7: W14

JD7: U14

JE7: V13

JF7: MIO-0

JA8: L15

JB8: Y19

JC8: Y14

JD8: U15

JE8: U17

JF8: MIO-9

JA9: J16

JB9: W18

JC9: T12

JD9: V17

JE9: T17

JF9: MIO-14

JA10: J14

JB10: W19

JC10: U12

JD10: V18

JE10: Y17

JF10: MIO-15

Table 9. Pmod pinout.

Digilent produces a large collection of Pmod accessory boards that can attach to the Pmod expansion connectors
to add ready-made functions like A/D’s, D/A’s, motor drivers, sensors, and other functions. See
www.digilentinc.com for more information.
The ZYBO has six Pmod connectors, some of which behave differently than others. Each Pmod connector falls into
one of four categories: standard, MIO connected, XADC, or high-speed Table 9 specifies which category each Pmod
falls into, and also lists the Zynq pins they are connected to. The following sections describe the different types of
Pmods.

16.1 Standard Pmod
The standard Pmod connector is connected to the PL of the Zynq via 200 Ohm series resistors. The series resistors
prevent short circuits that can occur if the user accidently drives a signal that is supposed to be used as an input.
The downside to this added protection is that these resistors can limit the maximum switching speed of the data
signals. If the Pmod being used does not require high-speed access, then the standard Pmod connector should be
used to help prevent damage to the devices.

16.2 MIO Pmod
The MIO Pmod connector is connected to the MIO bus in the PS of the Zynq via 200 Ohm series resistors. Like the
standard Pmod connector, these series resistors add protection at the cost of maximum switching speed. Since
these data signals are connected to the MIO interface, they can only be accessed by the PS peripheral controller
cores. The GPIO, UART, I2C, and SPI cores can all be used to drive devices connected to this Pmod. Note that the
pin layout of the UART and I2C cores will not align perfectly with the typical Pmod pinouts for these interfaces. This
means that UART or I2C devices connected to this Pmod may require some of the pins to be swapped around
externally using individual wires between the ZYBO and the Pmod.

16.3 Dual Analog/Digital Pmod (XADC Pmod)
The on-board Pmod expansion connector labeled “JA” is wired to the auxiliary analog input pins of the PL.
Depending on the configuration, this connector can be used to input differential analog signals to the analog-todigital converter inside the Zynq (XADC). Any or all pairs in the connector can be configured either as analog input
or digital input-output.

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ZYBO™ FPGA Board Reference Manual
In analog input mode, the voltage on these pins must be limited to 1V peak-to-peak. In digital mode, the regular
VCCO-dependent limits apply. See Xilinx datasheets for more information.
The Dual Analog/Digital Pmod on the ZYBO differs from the rest in the routing of its traces. The eight data signals
are grouped into four pairs, with the pairs routed closely coupled for better analog noise immunity. Pins 1 and 7,
pins 2 and 8, pins 3 and 9, and pins 4 and 10 are paired up. Furthermore, each pair has a partially loaded anti-alias
filter laid out on the PCB. The filter does not have capacitors C94-C97. In designs where such filters are desired, the
capacitors can be manually loaded by the user.
NOTE: The coupled routing and the anti-alias filters might limit the data speeds when used for digital signals.
The XADC core within the Zynq is a dual channel 12-bit analog-to-digital converter capable of operating at 1 MSPS.
Either channel can be driven by any of the auxiliary analog input pairs connected to the JXADC header. The XADC
core is controlled and accessed from the PL via the Dynamic Reconfiguration Port (DRP). The DRP also provides
access to voltage monitors that are present on each of the FPGA’s power rails, and a temperature sensor that is
internal to the FPGA. For more information on using the XADC core, refer to the Xilinx document titled “7 Series
FPGAs and Zynq-7000 All Programmable SoC XADC Dual 12-Bit 1 MSPS Analog-to-Digital Converter.” It is also
possible to access the XADC core directly using the PS, via the “PS-XADC” interface. This interface is described in
full in chapter 30 of the Zynq Technical Reference Manual.

16.4 High-Speed Pmod
The High-speed Pmods use the standard Pmod connector, but have their data signals routed as impedance
matched differential pairs for maximum switching speeds. They have pads for loading resistors for added
protection, but the ZYBO ships with these loaded as 0-Ohm shunts. With the series resistors shunted, these Pmods
offer no protection against short circuits, but allow for much faster switching speeds. The signals are paired to the
adjacent signals in the same row: pins 1 and 2, pins 3 and 4, pins 7 and 8, and pins 9 and 10.
Traces are routed 100 ohm (+/- 10%) differential.
These connectors should be used only when high speed differential signaling is required or the other Pmods are all
occupied. If used as single-ended, coupled pairs will have significant crosstalk. In applications where this is a
concern, the standard Pmod connector shall be used. Another option would be to ground one of the signals (drive
it low from the FPGA) and use its pair for the signal-ended signal.
Since the High-Speed Pmods have 0-ohm shunts instead of protection resistors, the operator must take precaution
to ensure that they do not cause any shorts.

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