Icarus Verilog vvp runtime engine man-page
vvp(1) $Date: 2005/01/29 06:28:19 $ vvp(1)
vvp - Icarus Verilog vvp runtime engine
vvp [-sv] [-Mpath] [-mmodule] [-llogfile] inputfile [extended-args...]
vvp is the run time engine that executes the default compiled form gen-
erated by Icarus Verilog. The output from the iverilog command is not
by itself executable on any platform. Instead, the vvp program is
invoked to execute the generated output file.
vvp accepts the following options:
This flag specifies a logfile where all MCI <stdlog> output
goes. Specify logfile as â€™-â€™ to send log output to <stderr>.
$display and friends send their output both to <stdout> and
-Mpath This flag adds a directory to the path list used to locate VPI
modules. The default path includes only the install directory
for the system.vpi module, but this flag can add other directo-
ries. Multiple paths are allowed, and modules will be searched
Tell the vvp run time to load the named module before executing
the simulation. The system.vpi module is loaded by default, but
additional modules, including modules that you compiled
locally, can be specified with this flag. Any number of modules
can be loaded, and they will be linked in the order they are
listed on the command line.
Normally, you only need to specify the name of the module,
without any directory path or .vpi suffix and the search path
is scanned to find the module. However, if the name includes at
least one directory character, then the search path is not
scanned and the name is assumed to be a complete file name.
-s Stop. This will cause the simulation to stop in the beginning,
before any events are scheduled. This allows the interactive
user to get hold of the simulation just before it starts.
-v Turn on verbose messages. This will cause information about run
time progress to be printed to standard out.
The vvp options described above must come before the design file name.
After the design file name, however, there may be any number of unspec-
ified arguments. These arguments are not interpreted by vvp but are
instead passed on to the executed design, and are available via the
$test$plusargs and $value$plusargs system functions.
Arguments that do not start with the plus(+) character are not avail-
able to the $plusargs system tasks, but can still be accessed via PLI
code via the vpi_get_vlog_info function. This means that vpi modules
may use arguments that do not start with + and be assured that they do
not interfere with user defined plus-args.
There are a few extended arguments that are interpreted by the standard
system.vpi module, which implements the standard system tasks and so is
always included. These arguments are described here.
This extended argument sets the wave dump format to VCD. This
is the default in the absence of any IVERILOG_DUMPER environ-
ment variable. The VCD dump files are large and ponderous, but
are also maximally compatible with third party tools that read
The -vcd-none variant actually suppresses all waveform output. This can
make long simulations run faster.
These extended arguments set the wave dump format to lxt, pos-
sibly with format optimizations. The -lxt-space flag sets the
output format to lxt with full compression enabled. The result-
ing files are quite small. The -lxt-speed chooses the lxt com-
pression mode that leads to the best execution time and the
fastest read time, at the expense of some file size.
The -lxt-none variant actually suppresses all waveform output. This can
make long simulations run faster.
-lxt2 The LXT2 format is slower then LXT (faster then VCD) but takes
less space, and is written out incrementally. Thus, you can
view lxt2 files while a simulation is still running (or paused)
or if your simulation crashes or is killed, you still have a
The vvp command also accepts some environment variables that control
its behavior. These can be used to make semi-permanent changes.
This selects the output format for the waveform output. Nor-
mally, waveforms are dumped in vcd format, but this variable
can be used to select lxt format, which is far more compact,
though limited to gtkwave or compatible viewers. It can also be
used to suppress VCD output, a time-saver for regression tests.
The simulation engine supports an interactive mode. The user may inter-
rupt the simulation (typically by typing Ctrl-C) to get to the interac-
tive prompt. From that prompt, the help command prints a brief summary
of the available commands.
The interactive mode may also be entered by a call to the $stop system
task from within the simulation, or by a call to the vpi_control VPI
function with the vpiStop control argument. These means of entering
interactive mode are equivalent.
Steve Williams (firstname.lastname@example.org)
iverilog(1), iverilog-vpi(1), <http://www.icarus.com/eda/verilog/>
Copyright Â© 2001-2003 Stephen Williams
This document can be freely redistributed according to the terms of the
GNU General Public License version 2.0
Version $Date: 2005/01/29 06:28:19 $ vvp(1)