replay_xreal :
A reproducer of an xreal-type signal stored in a waveform file.

The replay_xreal primitive replays an xreal-typed signal stored in a waveform file. This primitive is useful when composing a testbench that feeds the previously-collected simulation results as inputs to a new device-under-test (DUT).

For instance, to replay a signal with a hierarchical name of X1.Y1.a stored in a waveform file named mywaves.fsdb, you can instantiate this replay_xreal primitive with the parameters filename and signal defined as below:

    xreal a;
    replay_xreal #(.filename("mywaves.fsdb"), .signal("X1.Y1.a")) inst_replay (.out(a));

The replay_xreal primitive tries to reduce the number of events generated while keeping the error within the tolerance specified. The parameters abstol and reltol set the absolute and relative tolerances for this event-filtering, respectively.

Instead of replaying the whole waveform, you can replay a selected part of the waveform, of which start and stop time positions are defined by the parameters start and stop, respectively. For instance, if the parameter start is 100e-9 and stop is 200e-9, the replay_xreal primitive reproduces the waveform starting from the 100ns-position to the 200ns-position of the waveform, starting from the simulation time of zero. If the parameter start has a negative time value or the parameter delay has a positive time value, the primitive does not start replay until the simulation time of abs(start)+delay is elapsed and outputs a value defined by the parameter init_value or the initial value of the waveform at time=0 until then. On the other hand, when the primitive stops replay because it reaches the end of the waveform or a positive time value defined by the parameter stop, the primitive outputs a value defined by the parameter final_value or holds the last value of the waveform until the simulation ends.

NOTE: The current release supports the replay of waveforms only in FSDB-format files.

Input/Output Terminals

Name	I/O	Type	Description
out	output	xreal	signal output

Parameters

Name	Type	Default	Unit	Description
filename	string	“”	None	waveform filename
signal	string	“”	None	signal name
abstol	real	1e-4	None	absolute tolerance for event-filtering
reltol	real	1e-2	None	relative tolerance for event-filtering
start	real	0.0	seconds	waveform time position to start replay
stop	real	-1.0	seconds	waveform time position to stop replay
delay	real	0.0	seconds	initial_delay before replay starts
init_value	real	`NaN	None	initial value before replay starts
final_value	real	`NaN	None	final value after replay stops