该用法的代码源自夏宇闻老师的教材。
源代码：
module traffic_lights;
reg clock, red, amber, green;
parameter on = , off = , red_tics = ,
amber_tics = , green_tics = ;
// initialize colors.
initial red = off;
initial amber = off;
initial green = off;
always begin // sequence to control the lights.
red = on; // turn red light on
light(red, red_tics); // and wait.
green = on; // turn green light on
light(green, green_tics); // and wait.
amber = on; // turn amber light on
light(amber, amber_tics); // and wait.
end
// task to wait for 'tics' positive edge clocks
// before turning 'color' light off.
task light;
output color;
input [:] tics;
begin
repeat (tics) @ (posedge clock);
color = off; // turn light off.
end
endtask
always begin // waveform for the clock.
# clock = ;
# clock = ;
end
endmodule // traffic_lights.
测试代码run.do：
vlib work
vlog -novopt traffic_lights.v
vsim -voptargs=+acc work.traffic_lights
add wave * run 1000us
测试代码自动运行run.bat：
vsim -do run.do
运行结果如下：
