datapath unit: GCD calculator project

[jessy_kjl]

hi, i need help with my vhdl code:

entity DU is
Port ( gcd_inA, gcd_inB : in STD_LOGIC_VECTOR (3 downto 0);
selP0 : in STD_LOGIC;
selQ0 : in STD_LOGIC;
ldP : in STD_LOGIC;
ldQ : in STD_LOGIC;
ldG : in STD_LOGIC;
reset : in STD_LOGIC;
clrG : in STD_LOGIC;
opcode : in STD_LOGIC_VECTOR (1 downto 0);
clk : in STD_LOGIC;
gcd_out : out STD_LOGIC_VECTOR (3 downto 0);
Eq : out STD_LOGIC;
Lt : out STD_LOGIC;
data_outP, data_outQ, alu_out : buffer STD_LOGIC_VECTOR (3 downto 0));
end DU;

architecture Behavioral of DU is

begin

regP: process (ldP,selP0,clk,gcd_inA)
begin
if reset='1' then
data_outP <= "0000";
elsif clk'event and clk='1' then
if ldP ='1' then
if selP0 = '1' then
data_outP <= gcd_inA;
end if;
end if;
end if;
end process regP;

regQ: process (ldQ,selQ0,clk,gcd_inB)
begin
if reset='1' then
data_outQ <= "0000";
elsif clk'event and clk='1' then
if ldQ='1' then
if selQ0 = '1' then
data_outQ <= gcd_inB;
end if;
end if;
end if;
end process regQ;

regG: process (ldG,clrG,clk)
begin
if clrG='1' then
gcd_out <= "0000";
elsif clk'event and clk='1' then
if ldG='1' then
gcd_out <= data_outP;
end if;
end if;
end process regG;

ALU_module: process(data_outP,data_outQ,opcode)
begin
case opcode is
when "00" =>
alu_out <= data_outQ - data_outP;
when "01" =>
alu_out <= data_outQ - data_outQ;
when "10" =>
alu_out <= data_outP - data_outP;
when others =>
alu_out <= data_outP - data_outQ;
end case;
end process ALU_module;

--comparator;
Eq <= '1' when data_outP = data_outQ else '0' ;
Lt <= '1' when data_outP < data_outQ else '0' ;

end Behavioral;


in the rtl schematic, the buffers appear as output. why is this so?
thanks in advance!

 

[aredill]

I think this project belong to UMP lecturer. Are you trying to violate the engineering ethics? Good luck trying on your own.

 

[jessy_kjl]

I think this project belong to UMP lecturer. Are you trying to violate the engineering ethics? Good luck trying on your own.

yes, it is a labsheet given by my lecturer and since i am out of idea despite many attempts, here i am, seeking help. isn't it what this forum's all about? to discuss and share? fyi i came up with the coding myself with of course some assistance with from friends. therefore, i really do not think that i've violated the engineering ethics.

cheers ;p

 

[aredill]

hehe....jess lyn eh?
juz kidding maa.....dun emo2.