Introduction

Traffic lights are ubiquitous in modern America. They are essential in areas where many people are driving personal motor vehicles to get from place to place. Streets and thoroughfares represent a limited resource that must be managed if motorists are to be able to arrive at their intended destination both safely and expediently. This exercise will allow you to design a circuit which simulates a traffic light.

Specifications

• There will be two signals, each with a Red, Yellow, and Green light.
• Label one signal Zero and other One.
• You may use either the LED's provided in MMLogic, or the bitmap graphics included in this ZIP file.
• Stack the lights one on top of the other like this:

  Zero

• And they should work like this:

  Zero

  One

• The on time of each of the Green and Yellow lamps should be independantly adjustable.
• Following a Yellow light, both Reds should come on for a period of time, also independantly adjustable.
• As in a real traffic signal, the sequence of the lights should be:

  Light Zero	Light One
  Red	Red
  Green	Red
  Yellow	Red
  Red	Red
  Red	Green
  Red	Yellow
  Repeat

• The length of time both Reds are on can be controled with a single dial.
• The time base is the MMLogic Timer. Then, using counters, divide this frequency down to provide the necessary on times.
• It isn't necessary to to run the simulation "real time." The object is to build a circuit which could generate the proper timings.

Your Challenge

Using Multi Media Logic, design and implement a digital circuit to implement a traffic light timing generator according to this specification.