ModelSim SE User's Manual - Electrical and Computer Engineering

UM-232 8 - WLF files (datasets) and virtuals
Collapsing time and delta steps
ModelSim SE User’s Manual
By default ModelSim collapses delta steps. This means each logged signal that has events
during a simulation delta has its final value recorded to the WLF file when the delta has
expired. The event order in the WLF file matches the order of the first events of each signal.
You can configure how ModelSim collapses time and delta steps using arguments to the
vsim command (CR-373) or by setting the WLFCollapseMode (UM-534) variable in the
modelsim.ini file. The table below summarizes the arguments and how they affect event
recording.
vsim argument effect modelsim.ini setting
-wlfnocollapse All events for each logged signal are recorded to the
WLF file in the exact order they occur in the
simulation.
-wlfdeltacollapse Each logged signal which has events during a
simulation delta has its final value recorded to the
WLF file when the delta has expired. Default.
-wlftimecollapse Same as delta collapsing but at the timestep
granularity.
WLFCollapseMode = 0
WLFCollapseMode = 1
WLFCollapseMode = 2
When a run completes that includes single stepping or hitting a breakpoint, all events are
flushed to the WLF file regardless of the time collapse mode. It’s possible that single
stepping through part of a simulation may yield a slightly different WLF file than just
running over that piece of code. If particular detail is required in debugging, you should
disable time collapsing.