ModelSim SE User's Manual - Electrical and Computer Engineering

UM-426 17 - Signal Spy
Related procedures
Limitations
Example
ModelSim SE User’s Manual
Name Type Description
cancel_period time Optional. Cancels the signal_force command
after the specified period of time units.
Cancellation occurs at the last simulation
delta cycle of a time unit. A value of zero
cancels the force at the end of the current time
period. Default is -1 ms. A negative value
means that the force will not be cancelled.
verbose integer Optional. Possible values are 0 or 1. Specifies
whether you want a message reported in the
Transcript stating that the value is being
forced on the dest_object at the specified time.
Default is 0, no message.
init_signal_driver (UM-419), init_signal_spy (UM-422), signal_release (UM-427)
You cannot force bits or slices of a register; you can force only the entire register.
library IEEE, modelsim_lib;
use IEEE.std_logic_1164.all;
use modelsim_lib.util.all;
entity testbench is
end;
architecture only of testbench is
begin
force_process : process
begin
signal_force("/testbench/uut/blk1/reset", "1", 0 ns, freeze, open, 1);
signal_force("/testbench/uut/blk1/reset", "0", 40 ns, freeze, 2 ms, 1);
wait;
end process force_process;
...
end;
The above example forces reset to a "1" from time 0 ns to 40 ns. At 40 ns, reset is forced
to a "0", 2 ms after the second signal_force call was executed.
If you want to skip parameters so that you can specify subsequent parameters, you need to
use the keyword "open" as a placeholder for the skipped parameter(s). The first
signal_force procedure illustrates this, where an "open" for the cancel_period parameter
means that the default value of -1 ms is used.