Virtex-4 devices are user-programmable gate arrays with various configurable elements and embedded cores optimized for high-density and high-performance system designs. Virtex-4 devices implement the following functionality:

• I/O blocks provide the interface between package pins and the internal configurable logic. Most popular and
leading-edge I/O standards are supported by programmable I/O blocks (IOBs). The IOBs are enhanced for
source-synchronous applications. Source-synchronous optimizations include per-bit deskew,
data serializer/deserializer, clock dividers, and dedicated local clocking resources.

• Configurable Logic Blocks (CLBs), the basic logic elements for Xilinx FPGAs, provide combinatorial and
synchronous logic as well as distributed memory and SRL16 shift register capability.

• Block RAM modules provide flexible 18Kbit true dual-port RAM, that are cascadable to form larger
memory blocks. In addition, Virtex-4 FPGA block RAMs contain optional programmable FIFO logic for
increased device utilization.

• Cascadable embedded XtremeDSP slices with 18-bit x 18-bit dedicated multipliers, integrated Adder, and
48-bit accumulator.

• Digital Clock Manager (DCM) blocks provide self-calibrating, fully digital solutions for clock
distribution delay compensation, clock multiplication/division, and coarse-/fine-grained clock
phase shifting.