Digilent Basys 2 Referentiehandleiding - Pagina 2

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Basys2™ FPGA Board Reference Manual

The Basys 2 board is designed to work with the free ISE WebPack CAD software from Xilinx. WebPack can be used

to define circuits using schematics or HDLs, to simulate and synthesize circuits, and to create programming files.

WebPack can be downloaded free of charge from www.xilinx.com/ise/.

The Basys 2 board ships with a built-in self-test/demo stored in its ROM that can be used to test all board features.

To run the test, set the Mode Jumper (see below) to ROM and apply board power. If the test is erased from the

ROM, it can be downloaded and reinstalled at any time. See

documentation, reference designs, and tutorials.

Board Power

The Basys 2 board is typically powered from a USB cable, but a battery

connector is also provided so that external supplies can be used. To use USB

power, simply attach the USB cable. To power the Basys 2 using a battery or

other external source, attach a 3.5V-5.5V battery pack (or other power

source) to the 2-pin, 100-mil spaced battery connector (three AA cells in

series make a good 4.5+/- volt supply). Voltages higher than 5.5V on either

power connector may cause permanent damage.

Input power is routed through the power switch (SW8) to the four 6-pin

expansion connectors and to a Linear Technology LTC3545 voltage

regulator. The LTC3545 produces the main 3.3V supply for the board, and it

also produces 2.5V and 1.2V supply voltages required by the FPGA. Total

board current is dependent 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 100mA of current is drawn from the 1.2V supply, 50mA from the 2.5V supply, and 50mA from

the 3.3V supply. Required current will increase if larger circuits are configured in the FPGA, or if peripheral boards

are attached.

The Basys 2 board uses a four layer PCB, with the inner layers dedicated to VCC and GND planes. The FPGA and the

other ICs on the board have large complements of ceramic bypass capacitors placed as close as possible to each

VCC pin, resulting in a very clean, low-noise power supply.

Configuration

After power-on, the FPGA on the Basys 2 board must be configured before it can perform any useful functions.

During configuration, a "bit" file is transferred into memory cells within the FPGA to define the logical functions

and circuit interconnects. The free ISE/WebPack CAD software from Xilinx can be used to create bit files from

VHDL, Verilog, or schematic-based source files.

Digilent's PC-based program called Adept can be used to configure the FPGA with any suitable bit file stored on the

computer. Adept uses the USB cable to transfer a selected bit file from the PC to the FPGA (via the FPGA's JTAG

programming port). Adept can also program a bit file into an on-board non-volatile ROM called "Platform Flash".

Once programmed, the Platform Flash can automatically transfer a stored bit file to the FPGA at a subsequent

power-on or reset event if the Mode Jumper (JP3) is set to ROM. The FPGA will remain configured until it is reset

by a power-cycle event. The Platform Flash ROM will retain a bit file until it is reprogrammed, regardless of power-

cycle events.

Other product and company names mentioned may be trademarks of their respective owners.

Basys 2

for the test project as well as further

Figure 2. Basys 2 power circuits.

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