Basys2™ 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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To program the Basys 2 board, set the mode jumper
to PC and attach the USB cable to the board. Start
the Adept software, and wait for the FPGA and the
Platform Flash ROM to be recognized. Use the
browse function to associate the desired .bit file
with the FPGA, and/or the desired .mcs file with the
Platform Flash ROM. 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. The “Status
LED” LED (LD_8) will also blink after the FPGA has
been successfully configured. For further
information on using Adept, please see the Adept
documentation available at the Digilent website.
3
Oscillators
The Basys 2 board includes a primary, user-settable silicon
oscillator that produces 25MHz, 50MHz, or 100MHz based
on the position of the clock select jumper at JP4. Initially,
this jumper is not loaded and must be soldered in place. A
socket for a second oscillator is provided at IC6 (the IC6
socket can accommodate any 3.3V CMOS oscillator in a half-
size DIP package).
The primary and secondary oscillators are
connected to global clock input pins at pin B8 and pin M6
respectively.
Both clock inputs can drive the clock synthesizer DLL on the
Spartan 3E, allowing for a wide range if internal frequencies,
from 4 times the input frequency to any integer divisor of
the input frequency.
The primary silicon oscillator is flexible and inexpensive, but
it lacks the frequency stability of a crystal oscillator. Some
circuits that drive a VGA monitor may realize a slight
improvement in image stability by using a crystal oscillator
installed in the IC6 socket. For these applications, a 25MHz
(or 50MHz) crystal oscillator, available from any catalog
distributor, is recommended (see for example part number SG-8002JF-PCC at
www.digikey.com
).
XCF02
Platform
Flash
J
T
A
G
Spartan 3E
FPGA
Mode
Jumper
PC ROM
USB miniB
connector
Atmel
AT90USB2
Slave
serial
port
JTAG
port
LD8
Figure 4. Basys 2 Programming Circuits.
Spartan-3E
FPGA
B8
CLK_OUT
Linear Tech.
LTC6905
Oscillator
Frequency
Select
Jumper
25MHz
50MHz
100MHz
Figure 5. Basys 2 oscillator circuits.
