how to extend delay

Altera_Forum · ‎02-09-2011

How do i create delay for the output in the waveform?

Currently i'm having half a cycle delay, i want to increase it to 1 cycle.

(i have circled the area in the picture attatched)

And also, how do i make the period of the output to be 3 times the size of 1 clock period?

(i have also attatched the expected outcome)

This is what i have till now...

library ieee;

use ieee.std_logic_1164.all;

--------------------------------------------------------

ENTITY traffic_light IS

PORT(sensor : IN std_logic;

clock : IN std_logic;

red_light : OUT std_logic;

green_light : OUT std_logic;

yellow_light : OUT std_logic);

END traffic_light;

ARCHITECTURE simple OF traffic_light IS

TYPE t_state is (red, green, yellow);

SIGNAL present_state, next_state : t_state;

BEGIN

PROCESS(present_state, sensor)

BEGIN

CASE present_state IS

WHEN green =>

next_state <= yellow;

red_light <= '0';

green_light <= '1';

yellow_light <= '0';

WHEN red =>

red_light <= '1';

green_light <= '0';

yellow_light <= '0';

IF (sensor = '1') THEN

next_state <= green;

ELSE

next_state <= red;

END IF;

WHEN yellow =>

red_light <= '0';

green_light <= '0';

yellow_light <= '1';

next_state <= red;

END CASE;

END PROCESS;

PROCESS

BEGIN

WAIT UNTIL clock'EVENT and clock = '1';

present_state <= next_state;

END PROCESS;

END simple;

Please help!!

Altera_Forum · ‎02-09-2011

Usually, the way to extend signals is to add counters, and then inside the state machine wait till that counter gets to the correct value.

Altera_Forum · ‎02-09-2011

--- Quote Start ---

Usually, the way to extend signals is to add counters, and then inside the state machine wait till that counter gets to the correct value.

--- Quote End ---

So does that mean i have to add counter to extend the output delay? and also the period of the output waveform? i'm sorry don't quite get what u mean... :confused:

Altera_Forum · ‎02-09-2011

Yes add a counter, then in your state machine do something like this:


WHEN red => 
           red_light <= '1'; 
           green_light <= '0'; 
           yellow_light <= '0'; 
           IF (sensor = '1') and counter = 3 THEN 
              next_state <= green; 
           ELSE 
              next_state <= red;

Altera_Forum · ‎02-09-2011

i guess i need to declare the "counter" at the top right? thanks i'll try it out