verilog之task用法实例
该用法的代码源自夏宇闻老师的教材。
源代码：
1 module traffic_lights; 2 reg clock, red, amber, green; 3 parameter on = 1, off = 0, red_tics = 350, 4 amber_tics = 30, green_tics = 200; 5 // initialize colors. 6 initial red = off; 7 initial amber = off; 8 initial green = off; 9 always begin // sequence to control the lights. 10 red = on; // turn red light on 11 light(red, red_tics); // and wait. 12 green = on; // turn green light on 13 light(green, green_tics); // and wait. 14 amber = on; // turn amber light on 15 light(amber, amber_tics); // and wait. 16 end 17 // task to wait for 'tics' positive edge clocks 18 // before turning 'color' light off. 19 task light; 20 output color; 21 input [31:0] tics; 22 begin 23 repeat (tics) @ (posedge clock); 24 color = off; // turn light off. 25 end 26 endtask 27 always begin // waveform for the clock. 28 #100 clock = 0; 29 #100 clock = 1; 30 end 31 endmodule // traffic_lights.
测试代码run.do：
1 vlib work 2 vlog -novopt traffic_lights.v 3 vsim -voptargs=+acc work.traffic_lights 4 add wave * 5 6 run 1000us
测试代码自动运行run.bat：
1 vsim -do run.do
运行结果如下：
