R
Virtex-II Platform FPGAs: Functional Description
Configuration
Virtex-II devices are configured by loading application spe-
cific configuration data into the internal configuration mem-
ory. Configuration is carried out using a subset of the device
pins, some of which are dedicated, while others can be
re-used as general purpose inputs and outputs once config-
uration is complete.
DIN input pin a short time before each rising edge of the
externally generated CCLK.
Multiple FPGAs can be daisy-chained for configuration from
a single source. After a particular FPGA has been config-
ured, the data for the next device is routed internally to the
DOUT pin. The data on the DOUT pin changes on the falling
edge of CCLK.
Depending on the system design, several configuration
modes are supported, selectable via mode pins. The mode
pins M2, M1 and M0 are dedicated pins. The M2, M1, and
M0 mode pins should be set at a constant DC voltage level,
either through pull-up or pull-down resistors, or tied directly
Slave-serial mode is selected by applying <111> to the
mode pins (M2, M1, M0). A weak pull-up on the mode pins
makes slave serial the default mode if the pins are left
unconnected.
to ground or V
. The mode pins should not be toggled
CCAUX
Master-Serial Mode
during and after configuration.
In master-serial mode, the CCLK pin is an output pin. It is
the Virtex-II FPGA device that drives the configuration clock
on the CCLK pin to a Xilinx Serial PROM which in turn feeds
bit-serial data to the DIN input. The FPGA accepts this data
on each rising CCLK edge. After the FPGA has been
loaded, the data for the next device in a daisy-chain is pre-
sented on the DOUT pin after the falling CCLK edge.
An additional pin, HSWAP_EN is used in conjunction with
the mode pins to select whether user I/O pins have pull-ups
during configuration. By default, HSWAP_EN is tied High
(internal pull-up) which shuts off the pull-ups on the user I/O
pins during configuration. When HSWAP_EN is tied Low,
user I/Os have pull-ups during configuration. Other dedi-
cated pins are CCLK (the configuration clock pin), DONE,
PROG_B, and the Boundary-Scan pins: TDI, TDO, TMS,
and TCK. Depending on the configuration mode chosen,
CCLK can be an output generated by the FPGA, or an input
accepting an externally generated clock. The configuration
The interface is identical to slave serial except that an inter-
nal oscillator is used to generate the configuration clock
(CCLK). A wide range of frequencies can be selected for
CCLK which always starts at a slow default frequency. Con-
figuration bits then switch CCLK to a higher frequency for
the remainder of the configuration.
pins and Boundary-Scan pins are independent of the V
.
CCO
The auxiliary power supply (V
) of 3.3V is used for
CCAUX
these pins. All configuration pins are LVTTL 12 mA. (See
Virtex-II DC Characteristics in Module 3.)
Slave SelectMAP Mode
The SelectMAP mode is the fastest configuration option.
Byte-wide data is written into the Virtex-II FPGA device with
a BUSY flag controlling the flow of data. An external data
source provides a byte stream, CCLK, an active Low Chip
Select (CS_B) signal and a Write signal (RDWR_B). If
BUSY is asserted (High) by the FPGA, the data must be
held until BUSY goes Low. Data can also be read using the
SelectMAP mode. If RDWR_B is asserted, configuration
data is read out of the FPGA as part of a readback opera-
tion.
A persist option is available which can be used to force the
configuration pins to retain their configuration function even
after device configuration is complete. If the persist option is
not selected then the configuration pins with the exception
of CCLK, PROG_B, and DONE can be used as user I/O in
normal operation. The persist option does not apply to the
Boundary-Scan related pins. The persist feature is valuable
in applications which employ partial reconfiguration or
reconfiguration on the fly.
Configuration Modes
Virtex-II supports the following five configuration modes:
After configuration, the pins of the SelectMAP port can be
used as additional user I/O. Alternatively, the port can be
retained to permit high-speed 8-bit readback using the per-
sist option.
•
•
•
•
•
Slave-Serial Mode
Master-Serial Mode
Slave SelectMAP Mode
Master SelectMAP Mode
Boundary-Scan (JTAG, IEEE 1532) Mode
Multiple Virtex-II FPGAs can be configured using the
SelectMAP mode, and be made to start-up simultaneously.
To configure multiple devices in this way, wire the individual
CCLK, Data, RDWR_B, and BUSY pins of all the devices in
parallel. The individual devices are loaded separately by
deasserting the CS_B pin of each device in turn and writing
the appropriate data.
A detailed description of configuration modes is provided in
the Virtex-II User Guide.
Slave-Serial Mode
In slave-serial mode, the FPGA receives configuration data
in bit-serial form from a serial PROM or other serial source
of configuration data. The CCLK pin on the FPGA is an
input in this mode. The serial bitstream must be setup at the
Master SelectMAP Mode
This mode is a master version of the SelectMAP mode. The
device is configured byte-wide on a CCLK supplied by the
DS031-2 (v3.5) November 5, 2007
Product Specification
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Module 2 of 4
36
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