返回信息流LIBRARY IEEE;
USE IEEE.std_logic_1164.ALL;
ENTITY wzz IS
PORT(a : IN std_logic_vector(3 DOWNTO 0);
b : IN std_logic_vector(3 DOWNTO 0);
na : BUFFER std_logic_vector(3 DOWNTO 0);
nb : BUFFER std_logic_vector(3 DOWNTO 0);
sum : buffer std_logic_vector(3 downto 0);
sumttt : OUT std_logic_vector(3 downto 0);
sumone: OUT std_logic_vector(3 downto 0);
co : out std_logic
);
END wzz;
ARCHITECTURE BEHAVOR OF wzz IS
FUNCTION a8421_to_5221
(input: std_logic_vector(3 downto 0)) RETURN std_logic_vector is
VARIABLE result:std_logic_vector(3 downto 0);
begin
case input is
when "0100" => result:="0110";
when "0101" => result:="1000";
when "0110" => result:="1001";
when "0111" => result:="1100";
when "1000" => result:="1101";
when "1001" => result:="1110";
when OTHERS => result:=input;
end case;
return(result);
end a8421_to_5221;
FUNCTION a5221_to_8421
(input: std_logic_vector(3 downto 0)) RETURN std_logic_vector is
VARIABLE result:std_logic_vector(3 downto 0);
begin
case input is
when "0110" => result:="0100";
when "1000" => result:="0101";
when "1001" => result:="0110";
when "1010"|"1100" => result:="0111";
when "1011"|"1101" => result:="1000";
when "1110" => result:="1001";
when OTHERS => result:=input;
end case;
return(result);
end a5221_to_8421;
FUNCTION nf_add
(input1: std_logic_vector(3 DOWNTO 0); input2: std_logic_vector(3 DOWNTO 0)) RETURN std_logic_vector IS
VARIABLE nresult: std_logic_vector(4 downto 0);
VARIABLE m: integer RANGE 0 TO 3;
CONSTANT nS_vector: std_logic_vector(0 to 3) :="0101";
CONSTANT nCo_vector: std_logic_vector(0 to 3) :="0011";
VARIABLE ncin: std_logic:='0';
VARIABLE i:integer;
BEGIN
FOR i in 0 TO 3 LOOP
m:=0;
IF(input1(i)='1') THEN
m:=m+1;
END IF;
IF(input2(i)='1') THEN
m:=m+1;
END IF;
IF(nCin='1') THEN
m:=m+1;
END IF;
nresult(i) := nS_vector(m);
nCin := nCo_vector(m);
END LOOP;
RETURN(nresult);
END nf_add;
BEGIN
nb <= a8421_to_5221(b);
na <= a8421_to_5221(a);
PROCESS(na,nb)
VARIABLE cin,f1,f2: std_logic;
VARIABLE flag: std_logic_vector(3 downto 0):="0000";
VARIABLE n: integer RANGE 0 TO 3;
CONSTANT S_vector: std_logic_vector(0 to 3):= "0101";
CONSTANT Co_vector: std_logic_vector(0 to 3):= "0011";
variable result1 : std_logic_vector(3 downto 0);
VARIABLE i:integer;
BEGIN
f1:='0';
f2:='0';
cin:='0';
FOR i in 0 TO 3 LOOP
n:=0;
IF(na(i)='1') THEN
n:=n+1;
END IF;
IF(nb(i)='1') THEN
n:=n+1;
END IF;
IF(cin='1') THEN
n:=n+1;
END IF;
result1(i):=S_vector(n);
cin :=Co_vector(n);
IF(i=1) THEN f1:=cin; END IF;
IF(i=2) THEN f2:=cin; END IF;
END LOOP;
co<=cin;
sumone<=result1;
IF(f1='1') THEN
result1:=nf_add(result1,"0010"); END IF;
IF(f2='1') THEN
result1:=nf_add(result1,"1111"); END IF;
sum <= result1;
sumttt <= a5221_to_8421(sum);
end process;
END BEHAVOR;
这是一条镜像帖。来源：北邮人论坛 / circuit / #19200同步于 2011/12/1
Circuit机器人发帖
根据之前5221调整算法写的，但是结果不对，看结果应该是cin,f1,
danielinwind
2011/12/1镜像同步0 回复
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