Specifications
Development System Reference Guide www.xilinx.com 421
R
VHDL
VHDL is an acronym for VHSIC Hardware Description Language 
(VHSIC an acronym for Very High-Speed Integrated Circuits). It can 
be used to describe the concurrent and sequential behavior of a digital 
system at many levels of abstraction ranging from the algorithmic 
level to the gate level. VHDL is IEEE standard 1076-1993.
A VHDL file has a .vhd or .vhdl extension.
VITAL
VITAL is an acronym for VHDL Intitiative Toward ASIC Libraries. It 
is a VHDL-library standard (IEEE 1076.4) that defines standard 
constructs for simulation modeling, accelerating, and improving the 
performance of VHDL simulators.
W
wire 
A wire is a net or a signal. See net.
X
xtclsh
Xilinx Tcl Shell (xtclsh), which presents the xtclsh prompt used for 
running scripts and using the Xilinx Tcl commands.










