Technical data

Tcl/Tk and ModelSim
ModelSim EE/SE Tutorial 6-47
The custom-traffic-light interface
The subject of our main Tcl/Tk lesson is a simple traffic-light controller. The
system is comprised of three primary components: a state machine, a pair of traffic
lights, and a pair of traffic sensors. The components are described in three VHDL
files: traffic.vhd (the state machine), queue.vhd (the traffic arrival queue) and
tb_traffic.vhd (the testbench).
You could, of course, simulate this system with ModelSim’s familiar interface, but
Tcl/Tk provides us the option to try something different. Since we’re simulating
something most of us have seen and experienced before, we can create an intuitive
interface unique to the simulation.
Assumptions
The example assumes that source files were previously compiled. Here’s how it
works:
VHDL source files
describe the system
Tcl procedures create and
connect the interface, plus the
source files, to ModelSim
ModelSim commands are run
via the new interface using the
Tcl procedures
draw_intersection
traffic.vhd
queue.vhd
tb_traffic.vhd
connect_lights vsim -lib vhdl/work tb_traffic
examine -value <light_timing>
draw_queues
draw_controls force -freeze $var $val ns