Digilent D2-FT Referans Kılavuzu - Sayfa 2

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D2-FT Reference Manual

JTAG Scan Chain and Device Configuration

The Spartan 2E FPGA, the 18V00 ROM on the

D2-FT, and any programmable devices on

peripheral boards attached to the D2-FT can

be programmed via their JTAG ports. The

JTAG scan chain is routed to the FPGA, the

ROM, and around the board to four connection

ports as shown in Figure 2 below. The primary

configuration port (Port 1) uses a standard 6-

pin JTAG header (J7) that can accommodate

Digilent's JTAG3 cable (or cables from Xilinx or

other vendors). The other three JTAG

programming ports are bi-directional, and they

are available on the A1, B1, and C1 expansion

connectors. If no peripheral board is present, a

buffer on the D2-FT removes the expansion

connector from the JTAG chain. If a peripheral

board with a JTAG device is attached, the scan

chain is driven out the expansion connector so

that any JTAG-programmable parts can be

configured. If a Digilent port module is

connected to one of the three JTAG-enabled

expansion connectors, then the port module

can drive the JTAG chain to program all

devices in the scan chain (port modules

include Ethernet, USB, EPP parallel, and serial

modules -- see

www.digilentinc.com

information).

The scan chain can be driven from the primary

port by powering on the D2-FT, connecting it to

a PC with a JTAG programming cable, and

running the "auto-detect" feature of the

configuration software. The configuration

software allows devices in the scan chain to be

selectively programmed with any available

configuration file. If no programming ROM is

loaded in the IC5 socket (or if ROM is present

but is not to be included in the scan chain),

jumper-shunts must be loaded at JP1 and JP2

in the "Bypass ROM" location to route the

JTAG chain around the ROM socket. If an

18V02 (or larger) ROM is loaded in the IC5

socket, it can be included in the scan chain by

loading the JP1 and JP2 jumper-shunts in the

"Include ROM" positions.

If a programming ROM is present in the IC5

socket, the FPGA will automatically access the

ROM for configuration data if jumper shunts

www.digilentinc.com

are loaded in all three positions of J8 (M2, M1,

and M0).

Port modules attached to ports A1, B1, or C1

can drive the scan chain if a jumper-shunt is

installed on the primary JTAG header across

the TDI and TDO pins. In their default state,

Digilent port modules will appear as a JTAG

cable to the configuration software. Port

modules can disable their JTAG drivers; if

more than one JTAG driver is enabled on the

scan chain, programming may fail.

ROM bypass

jumpers

JTAG

connector

Cable bypass

jumper

Programming

mode select

jumpers

for more

Power Supplies

The D2-FT board uses two LM317 voltage

regulators to produce a 1.8VDC supply for the

Spartan 2E core, and 3.3VDC supply for the

I/O ring. Both regulators have good bypass

capacitance, allowing them to supply up to

1.5A of current with less than 50mV of noise

(typical). Power can be supplied from a low-

cost wall transformer supply. The external

supply must use a 2.1mm center-positive

connector, and it must produce between 6VDC

and 12VDC of unregulated voltage.

The D2-FT uses a four layer PCB, with the

inner layers dedicated to VCC and GND

planes. Most of the VCC plane is at 3.3V, with

an island under the FPGA at 1.8V. The FPGA

and the other ICs on the board all have

0.047uF bypass capacitors placed as close as

possible to each VCC pin.

Port 2

18V

ROM

Port 1

Figure 2. JTAG Signal Routing on D2-FT

Digilent, Inc.

Spartan 2E

FT 256

Port 4

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