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Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

how to extend delay

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!!

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    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's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    --- 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's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    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's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

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