sel.vhd

智能化微机测量和控制技术的迅速发展和广泛应用己经渗透到国民经济的各个部门。不但国防技 术、航空、航天、铁路、冶金、化工等产业

-------------产生数码管的片选信号
library ieee; 
use ieee.std_logic_1164.all; 
use ieee.std_logic_unsigned.all; 
---------------------  
entity sel is 
port(clk:in std_logic; 
q:out std_logic_vector(2 downto 0)); 
end sel; 
-----------------------------  
architecture sel_arc of sel is 
begin 
process(clk) 
variable cnt:std_logic_vector(2 downto 0); 
begin 
if clk'event and clk='1'then    ---在每次时钟的上升沿，位选信号自增1
cnt:=cnt+1;             -----实现数码管0—7的选择
end if; 
q<=cnt; 
end process; 
end sel_arc;