Question

4. In this problem you will use CodeWarrior to develop the code to implement a three-light traffic signal. The program should do the following:

a. Turn on a green LED attached to Port B bit 2 for 60 seconds,

b. Turn off the green LED and turn on a yellow LED attached to Port B bit 1 for 30 seconds,

c. Turn off the yellow LED and turn on a red LED attached to Port B bit 0 for 60 seconds,

d. Turn off the red LED and repeat steps a through d continuously.

Start up CodeWarrior and configure it to run in the normal way for an absolute assembler in Full Chip Simulation mode. The code for a 1 ms delay loop is below: ldy #6000 loop: dey bne loop

Some useful instructions are on the next pages. If you think you need some instructions that don’t appear on the following pages just ask.

Note that you can test your code using CodeWarrior by entering small numbers for the loops (e.g., 6 in place of 6000) and stepping through your code in simulation mode to see if the appropriate bits are set and cleared at Port B. Be sure to replace the smaller numbers with the correct ones before submitting your solution.

Watch out for error messages, particularly relating to putting big numbers in small registers (e.g., >255 in an 8-bit register, or >65,535 in a 16-bit register).

When you’ve finished, save your CodeWarrior .asm file and send it to me along with your completed exam. Also cut and paste your code below, just in case.

Answer 1

int red =10;

int yellow=9;

int green=8;

void setup(){
    pinMode(red, OUTPUT);
    pinMode(yellow, OUTPUT);
    pinMode(green, OUTPUT);
}

void loop(){
    changeLights();
    delay(60000);
}

void changeLights(){
    // green on, yellow on for 60 seconds
    digitalWrite(green, HIGH);
    delay(60000);

    // turn off green, then turn yellow on for 30 seconds
    digitalWrite(green, LOW);
    digitalWrite(yellow, HIGH);
    delay(30000);

    // turn off green and yellow, then turn on red
    digitalWrite(yellow, LOW);
    digitalWrite(green, LOW);
    digitalWrite(red, HIGH);
    delay(60000);
}