// test bench for Lab 3 — write to file version
// CSE140L
// expanded version — try the simpler traffic_tb first if
// you do not pass this one
//`timescale 1ns/1ns
import light_package::*;
module lab3_part1_tb;
logic clk = 1’b0;
logic reset = 1’b1; // should put your design in all-red
logic ew_left_sensor = 1’b0, // left traffic on e-w street
ew_str_sensor = 1’b0, // thru traffic on e-w street
ns_sensor = 1’b0; // traffic on n-s street
colors ew_left_light, // left arrow e-w turn onto n-s
ew_str_light, // straight ahead e-w
ns_light; // n-s (no left/thru differentiation)
//typedef enum logic[1:0] {red,yellow,green} color;
// your controller goes here
// input ports = logics above
// output ports = colors (each 2 bits wide)
traffic_light_controller dut(.*);
int fi;
int test_cnt; // lets testbench track tests
initial begin
fi = $fopen(“lab3_part1_results.txt”,”w”);
$fdisplay(fi,”t t t e e n”); // header for y, g status display
$fdisplay(fi,”s l n w w s”);
$fdisplay(fi,” s l “);
$fmonitor(fi, “Test Case: %d”, test_cnt);
#20ns reset = 1’b0;
#10ns;
// Test EW_LEFT to EW_STR without more traffic
test_cnt++ ;
ew_left_sensor = 1’b1 ;
fork
begin
#10ns ew_str_sensor = 1’b1;
wait (ew_str_light == green);
#25ns ew_str_sensor = 1’b0;
end
begin
wait (ew_left_light == green);
#15ns ew_left_sensor = 1’b0 ;
end
join
#200ns;
// Now set traffic at NS. Green NS lasts past sensor falling
test_cnt++ ;
ns_sensor = 1’b1 ;
wait (ns_light == green);
#35ns ns_sensor = 1’b0 ;
#200ns;
// Check NS again, but hold for more than 5 cycles.
// NS should cycle green-yellow-red when side traffic appears
test_cnt++;
ns_sensor = 1’b1;
#100ns ew_left_sensor = 1’b1;
#200ns ns_sensor = 1’b0;
#10ns ew_left_sensor = 1’b0;
#200ns;
// All three sensors become 1 at once.
// EW_STR should come first, then LEFT, then NS
test_cnt++;
ew_left_sensor = 1’b1;
ew_str_sensor = 1’b1;
ns_sensor = 1’b1;
#1000ns;
ew_left_sensor = 1’b0;
#200ns;
ew_str_sensor = 1’b0;
ns_sensor = 1’b0;
#200ns;
// All
test_cnt++;
$stop;
end
always begin
#5ns clk = 1’b1;
#3ns;
// print active sensors into result file
if(ew_str_sensor)
$fwrite(fi,”es “);
else
$fwrite(fi,” “);
if(ew_left_sensor)
$fwrite(fi,”el “);
else
$fwrite(fi,” “);
if(ns_sensor)
$fwrite(fi,”ns “);
else
$fwrite(fi,” “);
// print yellow and green states into result file
case({ew_str_light,ew_left_light,ns_light})
{red,red,red} : $fdisplay(fi,” %t”,$time);
{yellow,red,red}: $fdisplay(fi,”sy %t”,$time);
{green,red,red} : $fdisplay(fi,”sg %t”,$time);
{red,yellow,red}: $fdisplay(fi,” ly %t”,$time);
{red,green,red} : $fdisplay(fi,” lg %t”,$time);
{red,red,yellow}: $fdisplay(fi,” ny %t”,$time);
{red,red,green} : $fdisplay(fi,” ng %t”,$time);
default : $fdisplay(fi,”***ERROR** %t”,$time);
endcase
#2ns clk = 1’b0;
end
endmodule