用vhdl语言实现8位并转串电路和串转并电路，求大神指导！！急用！！

Answer 1

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity sc is
port(clk,rxd:in std_logic;
data:out std_logic_vector(7 downto 0));
end sc;

architecture rt8251 of sc is
signal count:std_logic_vector(3 downto 0):="0000";
signal do_latch:std_logic_vector(7 downto 0);
signal d_fb:std_logic_vector(9 downto 0);
signal rxdf:std_logic;
signal rdfull:std_logic:='0';
begin
data<=do_latch;

P1:process(clk)
begin
if(clk'event and clk='1') then
if ((rxdf='1') and (count="1000") ) then
do_latch(7 downto 0)<=d_fb(7 downto 0);
rdfull<='1';
end if;
end if;
end process p1;

p2:process(clk)
begin
if(clk'event and clk='1') then
if(rxd='0')then
rxdf<='1';
elsif((rxdf='1') and (count="1000") ) then
rxdf<='0';
end if;
end if;
end process p2;

p3:process(clk)
variable scir:integer range 0 to 8;
variable scis:std_logic_vector(3 downto 0);
begin
if (clk'event and clk='1') then
if (rxdf='1') then
scir:=scir+1;
else
scir:=0;

end if;
end if;
scis:=conv_std_logic_vector(scir,4);
count<= scis;
end process p3;

p4: process(clk)
begin
case count is
when "0000"=> d_fb(0)<=rxd;
when "0001"=> d_fb(1)<=rxd;
when "0010"=> d_fb(2)<=rxd;
when "0011"=> d_fb(3)<=rxd;
when "0100"=> d_fb(4)<=rxd;
when "0101"=> d_fb(5)<=rxd;
when "0110"=> d_fb(6)<=rxd;
when "0111"=> d_fb(7)<=rxd;
when "1000"=> d_fb(8)<=rxd;
when others=> d_fb(9)<='1';
end case;
end process p4;
end rt8251;

转自：http://zhidao.baidu.com/question/229121509.html

Answer 2

可以参阅《VHDL数字系统设计》（科学出版社2009年出版）p.155~159，上面有完整的电路描述和仿真图。