verilogTown

a Verilog based game

Simulator - Understanding what's under the hood 

The more you understand about the verilogTown, the better you can design levels and solve them.  Here we will describe the car behaviour, simulator, and program structures.

Car Behaviour

If you have read the Verilog tutorial, you got some insight to how the cars in verilogTown behave.

The car will follow the following rules:

• Cars stay in their lanes (Right Lane convention).
• A car will not crash into a car that is moving in the same direction as it is.  Therefore, if car 1 stops at a traffic light going north, car 2 will stop behind car 1 if also going north.
• A car will follow the traffic signal that it goes through.  If it is a forced turn that is not legal, then the car will wait.  In the below example, A car can't turn left and is waiting, car B is forced to go straight, and car C can go any direction it wants.
• A car has a predefined destination and does a breadth-first-search to find a path.  It will follow that path until a traffic light forces it off that path.  If there is no solution for a new path then the car will count as an unsuccessful car.  Note, cars will do U-turns in traffic lights if this is the shortest path.

Simulator Details

Here are some facts about the simulator that you should understand:

• The simulator for the Verilog has a clock of 25Hz.  This means the clock ticks for every animation frame in the game.
• After each clock simulation, the game simulates the combinational logic to propogate results through the logic.
• The reset signal is handled for you and goes from low to high when the simulation starts.
• In the combinational template you might have the following situation:   where two cars are approaching the light at the same rate and the lights are currently set to Go.  You might think that the when these cars arrive at their respective sensors that the combinational logic will only allow one car through.  However, since both cars arrive at the sensor at the same time they check the traffic light, what will happen is both cars will continue forward assuming the light says Go before the logic changes the control (new inputs haven't propagated yet).  You can try this on Level 2 by making the upper left traffic light combinational and simulate this.  This combinational Verilog design prevents this.  

Program Structure - Editing Verilog Files and Levels

You might wonder where the Verilog files are kept and the levels.  This is all part of the distribution you downloaded, and both the xml files that represent the levels and the Verilog design files are in this.

To edit the Verilog files, from the root directory of verilogTown go to Levels/ and then go to the level you want to edit.  For example, to edit the traffic lights for Level 3 you would open the "Lv3/VerilogFiles/" directory.  There, you will see 11 files, which are the Verilog files.  We use the following convention for which file corresponds to which file (left to right, top to bottom):
You can edit these files using your own editor and enter these into other Verilog tools to run simulations.

Also in the directory "Lv3/Maps/" there is a file called "lv03.xml".  This file tells the game what the map looks like and where the cars come from.  You can edit this file, but we recommend using our level editor tool.

Copyright © 2014 Peter Jamieson. All Rights Reserved.