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additional tracing doc

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jand 2003-07-18 09:21:40 +00:00
parent ad188931c8
commit cf16756f91
1 changed files with 21 additions and 8 deletions
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doc/whatsnew03/whatsnew03.tex
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@ -32,8 +32,10 @@ sequence of generators. For example:
tb_fsm = testbench() tb_fsm = testbench()
\end{verbatim} \end{verbatim}
To enable VCD tracing, the instance should be created as The \code{tb_fsm} variable is subsequently passed
follows instead: as an argument to a \class{Simulation} object constructor
for simulation. To enable VCD tracing, the instance should
be created as follows instead:
\begin{verbatim} \begin{verbatim}
tb_fsm = trace_sigs(testbench) tb_fsm = trace_sigs(testbench)
@ -44,14 +46,25 @@ traced in an output VCD file called \file{tb_fsm.vcd}. Note that the
argument of \function{trace_sigs()} consists of the uncalled argument of \function{trace_sigs()} consists of the uncalled
function. By calling the function under its control, function. By calling the function under its control,
\function{trace_sigs()} gathers information about the hierarchy and \function{trace_sigs()} gathers information about the hierarchy and
the signals to be traced. the signals to be traced. In addition to a function argument,
\function{trace_sigs()} accepts an arbitrary number of non-keyword and
In addition, \function{trace_sigs()} accepts an arbitrary number of keyword arguments that will be passed to the function call.
additional non-keyword and keyword arguments that will be passed
to the function call.
The restrictions on VCD tracing are as follows. First, only
\class{Signal} objects can be traced. Second, only a hierarchy of
instances returned by a pre-simulation top level function call can be
traced. Also, all instances to be traced should have a name: this is
done by assigning the result of an instantiating function call to a
local variable (instead of using it directly.)
Signals are dumped in a suitable format. This format is inferred at
the \class{Signal} construction time, from the type of the initial
value. In particular, \class{bool} signals are dumped as single
bits. (This only works starting with Python2.3, when \class{bool} has
become a separate type). Likewise, \class{intbv} signals with a
defined bit width are dumped as bit vectors. To support the general
case, other types of signals are dumped as a string representation, as
returned by the standard \function{str()} function.
\end{document} \end{document}