Digilent 410-182P-KIT - Manual (Page 7)

Nexys3 Reference Manual
Doc: 502-182 page 7 of 22
I/O Expand
The I/O Expand tab works with an IP block in
the FPGA to provide additional simple I/O
beyond the physical devices found on the
Nexys3 board. Virtual I/O devices include a 24-
LED light bar, 16 slide switches, 16 push
buttons, 8 discrete LEDs, a 32-bit register that
can be sent to the FPGA, and a 32-bit register
that can be read from the FPGA. The IP block,
available in the Adept I/O Expansion reference
design (AdeptIOExpansion.zip) on the Adept
page of the Digilent website, provides a simple
interface with well-defined signals. This IP
block can easily be included in, and accessed
from, user-defined circuits.
For more information, see the Adept
documentation available at the Digilent
website.
Power Supplies
The Nexys3 board can receive power from the Adept USB port or from an external power supply.
Jumper JP1 (near the power jack) determines which source is used.
The USB port can deliver enough power for the vast majority of designs. It is possible that a very
demanding application, including an application that drives many peripheral boards, might require
more power than can be delivered by the USB port. Some applications may also need to run without
being connected to a PC’s USB port. In either case, an external power supply or battery pack can be
used by setting JP
1 to “Wall”.
The main regulator on the Nexys3 can accommodate input voltages up to 5.5VDC. An external DC
wall-plug supply should provide at least five watts of input power, and use a coax center-positive
2.1mm internal-diameter plug. An external battery pack
can also be used by connecting the battery’s
terminal leads to connector J11 (J11 is in parallel with the wall-plug power jack, so if a battery pack is
connected, a wall plug should not be). An external battery pack should also be limited to 5.5VDC, and
should be capable of delivering adequate power for the application.
Voltage regulator circuits from Linear Technology create the required 3.3V, 2.5V, 1.8V, and 1.2V
supplies from the main power input. The table below provides additional information (typical currents
depend strongly on FPGA configuration and the values provided are typical of medium size/speed
designs).