Technical data

Basic VHDL simulation

ModelSim EE Tutorial ModelSim EE Lessons

The

force

command you just invoked is interpreted by VSIM to mean:

• force clk to the value 1 at 50 ns after the current time

• then to 0 at 100 ns after the current time

• repeat this cycle every 100 ns

Note how the Run Length selector on the toolbar now indicates 100 (ns is the

current default resolution). You will see the effects of this

force

command as soon

as you tell the simulator to run.

Now you will exercise two different

Run

functions from buttons on the Main or Wave

window toolbar. Select the

Run

button first. When the run is complete, select

Run All

Run

. This causes the simulation to run and then stop after 100 ns.

(PROMPT: run 100) (MENU: Run > Run 100ns)

Run -All

. This causes the simulator to run forever. To stop the run, go

on to the next step.

(PROMPT: run -all) (MENU: Run > Run -All)