vvp - Online in the Cloud

PROGRAM:

NAME

vvp - Icarus Verilog vvp runtime engine

SYNOPSIS

vvp [-sv] [-Mpath] [-mmodule] [-llogfile] inputfile [extended-args...]

DESCRIPTION

vvp is the run time engine that executes the default compiled form generated 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.

OPTIONS

vvp accepts the following options:

-llogfile
This flag specifies a logfile where all MCI <stdlog> output goes. Specify logfile
as '-' to send log output to <stderr>. $display and friends send their output
both to <stdout> and <stdlog>.

-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 directories. Multiple paths are allowed, and modules will
be searched in order.

-mmodule
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.

-n This flag makes $stop or a <Control-C> a synonym for $finish. It can be used to
give the program a more meaningful interface when running in a non-interactive
environment.

-N This flag does the same thing as -n, but results in an exit code of 1 if the
stimulation calls $stop. It can be used to indicate a simulation failure when
running a testbench.

-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.

-V Print the version of the runtime, and exit.

EXTENDED ARGUMENTS

The vvp options described above must come before the design file name. After the design
file name, however, there may be any number of unspecified 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 available 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.

-vcd This extended argument sets the wave dump format to VCD. This is the default in
the absence of any IVERILOG_DUMPER environment variable. The VCD dump files are
large and ponderous, but are also maximally compatible with third party tools that
read waveform dumps.

-lxt|-lxt-speed|-lxt-space
These extended arguments set the wave dump format to lxt, possibly with format
optimizations. The -lxt-space flag sets the output format to lxt with full
compression enabled. The resulting files are quite small. The -lxt-speed chooses
the lxt compression mode that leads to the best execution time and the fastest
read time, at the expense of some file size.

-lxt2|-lx2
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 useful dump.

-none This flag can be used by itself or appended to the end of the above dumpers
(vcd/lxt/lxt2/lx2) to suppress all waveform output. This can make long simulations
run faster.

-sdf-warn
When loading an SDF annotation file, this option causes the annotator to print
warnings for questionable but non-fatal issues.

-sdf-info
When loading an SDF annotation file, this option causes the annotator to print
information about the annotation.

-sdf-verbose
This is shorthand for -sdf-info -sdf-warn.

ENVIRONMENT

The vvp command also accepts some environment variables that control its behavior. These
can be used to make semi-permanent changes.

IVERILOG_DUMPER=lxt|lxt2|lx2|vcd|none
This selects the output format for the waveform output. Normally, 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.

INTERACTIVE MODE

The simulation engine supports an interactive mode. The user may interrupt the simulation
(typically by typing <Control-C>) to get to the interactive 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.

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