Digilent Nexys Board - Manual (Page 3)

Digilent
Nexys Reference Manual
www.digilentinc.com
Copyright Digilent, Inc. Page 3/10 Doc: 502-107
The FPGA and the Platform Flash ROM can be programmed from a PC using Digilent’s Adept
software or Xilinx’s iMPACT software (both are available for free download). Digilent’s Adept Software
works with the USB circuit, and Digilent’s JTAG3 parallel cable is compatible with iMPACT. When
using the USB circuit, a “cable bypass” jumper must be loaded on the JTAG header at J6 to connect
the TDI and TDO signals.
To program the Nexys board, connect the programming cable to the board and to a PC, and apply
power to the board. Start the programming software, and wait for the FPGA and the Platform Flash
ROM to be automatically identified. To program the FPGA, select the desired .bit file; to program the
Platform Flash, select the desired .mcs file. Right-click on the device to be programmed, and select
the “program” function. The configuration file will be sent to the FPGA or Platform Flash, and the
software will indicate whether programming was successful. For more information on device
programming, refer to the Adept or iMPACT reference manual.
Both the FPGA and Platform Flash ROM will always appear in the scan chain. After the Platform
Flash ROM has been loaded with a configuration file, the FPGA can automatically load that file at
power-on if programming mode control jumper is loaded in the ROM position.
A reset button is provided (labeled “reset”) that can erase the configuration in the FPGA, and start a
new programming cycle. An LED labeled “done” will illuminate whenever the FPGA has been
successfully configured.
Power Supply
The Nexys board can be powered from the USB port or
any DC supply that produces a voltage in the 5VDC-
9VDC range. The power jack on the Nexys board
requires a center-positive, 2.1mm power supply
connector as is commonly found on wall-plug power
supplies. Voltages higher than 10V may permanently
damage Nexys.
The “raw” voltage from the power jack is routed to the
four 6-pin expansion connectors, the 16-pin expansion
connector, and to a 3.3V voltage regulator. The 2.5V
and 1.2V supplies required by the FPGA are generated
from the 3.3V supply. Total board current is dependant
on FPGA configuration, clock frequency, and external
connections. In test circuits with roughly 20K gates routed, a 50MHz clock source, and all LEDs
illuminated, about 200mA of current is drawn from the 1.2V supply, 50mA from the 2.5V supply, and
100mA from the 3.3V supply. Required current will increase if larger circuits are configured in the
FPGA, and if peripheral boards are attached. The table below summarizes the power supply
parameters.
Vendor Technology Use Supply PN Current (Max/typ)
Linear Technology Switcher Main power 3.3V (IC6) LTC1765 3A/100mA
Linear Technology Switcher (dual) FPGA Vaux 2.5V (IC7) LTC3417 1.4A/50mA
Linear Technology Switcher (dual) FPGA Vcore 1.2V (IC7) LTC3417 1.4A/200mA
Linear Technology Linear Vsram 1.8V (IC8) LTC1844 150mA/90mA
Linear Technology Linear Vusb 3.3V (IC4) LTC1844 150mA/60mA