1. Home
  2. Field-Programmable Gate Arrays
  3. switching problem

switching problem

Hello!

I'm trying to build the following thing: a 7-segment-led that increases its value every time a switch is pressed.

library IEEE; use IEEE.STD_LOGIC_1164.ALL; use IEEE.STD_LOGIC_ARITH.ALL; use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity sevsegment is Port ( clk_i: in std_logic; sevseg : out std_logic_vector(6 downto 0); reset : in std_logic; switch: in std_logic); end sevsegment;

architecture Behavioral of sevsegment is signal sevseg_s: std_logic_vector(6 downto 0); begin

process(reset,switch,clk_i) variable counter: integer range 0 to 9; begin if clk_i'event and clk_i='1' then if reset='0' then counter:=0; sevseg_s

Reply to
Simone Winkler
Loading thread data ...

Hello,

When you say, "Why doesn't it work?" it would be helpful to know what the failure mechanism is...

I wonder if this is a lab assignment gone wrong, or an astute application of reverse psychology to get an answer to a homework question? ;)

For what it's worth, I think you might go back and review how to describe a synchronous counter. Your code may simulate properly, but a synthesis tool may have a difficult time implementing it.

You could design a synchronous counter with no clock enable, where the switch signal is used as the clock, assuming you debounce it properly.

Or, you could design a synchronous counter that is clocked from a free-running clock, and you use the switch signal as a clock enable, assuming you debounce and synchronize it properly, and then detect transitions on the signal across clock cycles to generate a single "press" event that will allow the counter to increment only one time in response.

Eric

Sim>

Reply to
Eric Crabill

Hi Simone - As Eric suggested, there is code which simulates, but might not be synthesizeable. One problem area might be the use of multiple clocks. Switch does not need to be a clock in this case. The starting point would be to build a simple edge detect circuit for a normally HI signal, with low going pulse for an event capture.

q0_switch

its

Reply to
John Retta

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.