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Many of todays telecom and networking
systems use high-bandwidth interfaces
based on low voltage differential signaling
(LVDS) or other differential I/O standards.
Differential I/O standards simplify system
design by improving system performance
and signal integrity.
Protocols based on I/Os such as SPI-4.2,
SFI, RapidIO, and HyperTransport are
central to leading-edge system design. To
take advantage of these technologies, you
have to work through multiple challenges
to ensure device interoperability and standards
compliance.
Xilinx® provides Virtex-4 development
boards as well as standards-compliant
intellectual property (IP) cores and
free reference designs for major system
interface protocols. This allows you to
focus on user application design and not
worry about interoperability and standards
compliance.
With the Virtex-4 source-synchronous
interfaces tool kit, designing networking,
telecom, servers, and computing systems
has never been faster or easier.
The Virtex-4 ML450 source-synchronous
interfaces tool kit includes the following:
- Virtex-4 ML450 development board
(XC4VLX25FF668 FPGA)
- 5V/6.5 AC/DC power supply
- Country-specific power supply line cord
- RS232 serial cable, DB9-F to DB9-F
- Four clock module daughter boards
- Two sets of blue ribbon loopback
cables for LVDS testing
- Documentation and reference design
CD-ROM
The Virtex-4 ML450 Development Board
The main component in the Virtex-4
ML450 source-synchronous interfaces tool
kit is the ML450 development board
(Figure 1). Featuring a Virtex-4
XC4VLX25FF668 FPGA coupled to highspeed
connectors, this board supports the
development of high-speed interface
designs using several popular protocols.
The ML450 demonstration board is a
simple board providing several connector
interfaces to the FPGA. The board comprises
basic support circuitry, including power
regulators, a serial RS232 connector, a small
graphics LCD, a few user push buttons and
LEDs, and a DDR-1 SDRAM. These simple
peripherals allow a PC to communicate
with the FPGA and also provide basic input
and output indicators. Configuration is
enabled via a JTAG connector, or you can
use a System ACE CompactFlash card for
bitstream storage and loading.
We designed the board to demonstrate
the high-speed I/O capability of the Virtex-4
FPGA. Eighty differential channels are
pinned out to four Samtec connectors. Forty
pairs each are routed to two connectors on
either side of the FPGA, allowing you to designate
transmit and receive interfaces.
Two mini coax flat cables are provided with
the kit, enabling loopback of high-speed data
between transmit and receive connectors.
In addition to these differential signals,
another 32 pairs are routed to a
HyperTransport Consortium DUT (device
under test)-compliant connector, allowing
for the development of an interface to other
HyperTransport-based boards.
The ML450 evaluation platform supports
a wide range of communications standards,
including SFI-4. Figure 2 shows the user
interface of an SFI-4 demo running on an
ML450 board. The user interface includes a
bit error rate tester (BERT) that measures the
integrity of the data received from 16 LVDS
transmitters. You can select from several
pseudo-random bit sequences to simulate
data, and error counters on the user interface
maintain a running count of all bit errors
that occur during transmission. The BERT
also keeps track of which channels are receiving
errors to provide further troubleshooting
visibility in a multi-channel design.
In terms of performance, the ML450
platform supports a 16-channel single data
rate design (SDR) running up to 700 MHz
(Figure 3) and a 16-channel double data
rate (DDR) design running up to 500
MHz (Figure 4). The transmission medium
of the 16 channels consists of two
Samtec connectors, a 12-inch ribbon cable,
and 10 inches of FR4.
The ML450 also provides the ability to
command the supply rails of the FPGA to
assume ±5% of their nominal values. This
feature provides a convenient way for you
to stress your design and identify marginal
behavior. The voltages are controlled
through the user interface by simply moving
a slider button to the left or right. In
Figure 2, VccAux is raised to +5%, while
the other supplies remain nominal.
A small daughtercard that plugs onto
the board provides the high-speed clock
used by the SFI-4 design. This daughtercard
generates a programmable LVDS
clock between 200 MHz and 700 MHz,
eliminating the need for a cumbersome
bench-top pulse generator.
Board Features
The ML450 development board includes
the following:
- XC4VLX25FF668 FPGA
- Eight clock sources:
200 MHz and 250 MHz on-board
oscillators
Two sets of SMA differential clock
input connectors
Four Samtec clock module connectors
- One 64 x 128 pixel LCD
- One DB9-M RS232 port
- A System ACE CompactFlash configuration
controller that allows storing
and downloading of as many as eight
FPGA configuration image files
- Four LVDS Samtec connectors (a total
of 40 input channels and 40 output
channels)
- One HyperTransport connector
(HyperTransport Consortium
DUT connector-compliant)
- On-board power regulators
with ± 5% output margin test
capabilities
Clock Generation
The clock generation section of the
ML450 development board provides
all necessary clocks for the Virtex-4
FPGA. Eight clock sources are provided
as follows:
- Epson EG2121CA 2.5V 250
MHz differential low-voltage positive
emitter-coupled logic
(LVPECL) oscillator
- Epson EG2121CA 2.5V 200
MHz differential LVPECL
oscillator
- Two differential SMA clock
inputs
- Four Samtec user clock sockets
The differential SMA clock inputs
are connected to the global clock
inputs of the FPGA, accessing the
upper and lower halves. An on-board
200 MHz oscillator calibrates the I/O
delay, and an on-board 250 MHz
oscillator is provided for use with the
HyperTransport IP.
The four clock modules included
in the kit are:
- Type A: direct balanced differential
SMA input
- Type B: Epson EG2121CA 2.5V
400 MHz differential LVPECL
- Type C: ICS programmable, 200
MHz to 700 MHz
- Type D: unbalanced, single-ended
transformer coupled into LVDS
Note that all clock module daughter
board outputs are converted to
LVDS on the daughter boards.
SDRAM Memory
The ML450 development board
provides 64 MB of DDR-1 SDRAM
memory (Micron Semiconductor
MT46V32M16N-5B).
Liquid Crystal Display
The ML450 development board provides
an 8-bit interface to a 64 x 128 LCD
panel (DisplayTech Q64128E-FC-BC-3LP, 64 x 128).
RS232 Port
The ML450 development board
provides a DB9-M connection for a
simple RS232 port. The board uses
the Maxim MAX3316 device to
drive the RD, TD, RTS, and CTS
signals. You must provide a UART
core internal to the FPGA to enable
serial communication.
System ACE Interface
In addition to a JTAG configuration
connector, the ML450 development
board provides a System
ACE interface to configure the
Virtex-4 FPGA. The interface also
gives software designers the ability
to run code (for soft-processor IP
within the FPGA) from removable
CompactFlash cards.
LVDS Connectors
The ML450 development board
provides 40 channels of transmit
signals and 40 channels of receive
LVDS signals. These signals are
distributed across two Samtec
QSE-DP connectors for transmitting
and another two connectors
for receiving.
HyperTransport Connector
The ML450 development board provides
16 channels of transmit and
receive data, along with miscellaneous
control signals on the Samtec
QSE HyperTransport connector.
Conclusion
With the Virtex-4 source-synchronous
interfaces tool kit, designing
networking, telecom, servers, and
computing systems has never been
faster or easier.
For more information on the
demonstration board and the kit,
visit www.xilinx.com/ml450/.
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