Virtex™-E 1.8 V Extended Memory Field Programmable Gate Arrays
Module 2 of 4 www.xilinx.com DS025-2 (v3.0) March 21, 2014
12
R
— OBSOLETE — OBSOLETE — OBSOLETE — OBSOLETE —
tions and the desired performance. Finally, the router inter-
connects the blocks.
The PAR algorithms support fully automatic implementation
of most designs. For demanding applications, however, the
user can exercise various degrees of control over the pro-
cess. User partitioning, placement, and routing information
is optionally specified during the design-entry process. The
implementation of highly structured designs can benefit
greatly from basic floor planning.
The implementation software incorporates Timing Wizard
®
timing-driven placement and routing. Designers specify tim-
ing requirements along entire paths during design entry.
The timing path analysis routines in PAR then recognize
these user-specified requirements and accommodate them.
Timing requirements are entered on a schematic in a form
directly relating to the system requirements, such as the tar-
geted clock frequency, or the maximum allowable delay
between two registers. In this way, the overall performance
of the system along entire signal paths is automatically tai-
lored to user-generated specifications. Specific timing infor-
mation for individual nets is unnecessary.
Design Verification
In addition to conventional software simulation, FPGA users
can use in-circuit debugging techniques. Because Xilinx
devices are infinitely reprogrammable, designs can be veri-
fied in real time without the need for extensive sets of soft-
ware simulation vectors.
The development system supports both software simulation
and in-circuit debugging techniques. For simulation, the
system extracts the post-layout timing information from the
design database, and back-annotates this information into
the net list for use by the simulator. Alternatively, the user
can verify timing-critical portions of the design using the
TRCE
®
static timing analyzer.
For in-circuit debugging, an optional download and read-
back cable is available. This cable connects the FPGA in the
target system to a PC or workstation. After downloading the
design into the FPGA, the designer can single-step the
logic, readback the contents of the flip-flops, and so observe
the internal logic state. Simple modifications can be down-
loaded into the system in a matter of minutes.
Configuration
Virtex-E devices are configured by loading configuration
data into the internal configuration memory. Note that
attempting to load an incorrect bitstream causes configura-
tion to fail and can damage the device.
Some of the pins used for configuration are dedicated pins,
while others can be re-used as general purpose inputs and
outputs once configuration is complete.
The following are dedicated pins:
• Mode pins (M2, M1, M0)
• Configuration clock pin (CCLK)
•PROGRAM
pin
• DONE pin
• Boundary-scan pins (TDI, TDO, TMS, TCK)
Depending on the configuration mode chosen, CCLK can
be an output generated by the FPGA, or it can be generated
externally and provided to the FPGA as an input. The
PROGRAM
pin must be pulled High prior to reconfiguration.
Note that some configuration pins can act as outputs. For
correct operation, these pins require a V
CCO
of 3.3 V to per-
mit LVTTL operation. All of the pins affected are in banks 2
or 3. The configuration pins needed for SelectMap (CS,
Write) are located in bank 1.
Configuration Modes
Virtex-E supports the following four configuration modes.
• Slave-serial mode
• Master-serial mode
• SelectMAP mode
• Boundary-scan mode (JTAG)
The Configuration mode pins (M2, M1, M0) select among
these configuration modes with the option in each case of
having the IOB pins either pulled up or left floating prior to
configuration. The selection codes are listed in Ta bl e 8.
Configuration through the boundary-scan port is always
available, independent of the mode selection. Selecting the
boundary-scan mode simply turns off the other modes. The
three mode pins have internal pull-up resistors, and default
to a logic High if left unconnected. However, it is recom-
mended to drive the configuration mode pins externally.
Tabl e 8: Configuration Codes
Configuration Mode M2 M1 M0 CCLK Direction Data Width Serial D
out
Configuration Pull-ups
Master-serial mode 0 0 0 Out 1 Yes No
Boundary-scan mode 1 0 1 N/A 1 No No
SelectMAP mode 1 1 0 In 8 No No
Slave-serial mode 1 1 1 In 1 Yes No
Master-serial mode 1 0 0 Out 1 Yes Yes
剩余117页未读，继续阅读
