4bit transfer using synchronous d flip-flop( transfer 4bit from register a to register b)

Question

When I run this code two errors appear that say "Actual parameter type in port map does not match the type of the formal port 's'. I need help to understand how to fix these.

-- code that try in EDA playground to transfer from one register to another 

 -- library 
 library ieee;
 use ieee. std_logic_1164.all;


 -- declaration for d flip-flop
 entity D_FF is
 PORT( D : in std_logic_vector(7 downto 0);
       s :in std_logic; 
       CLOCK: in std_logic;
       Q: out std_logic_vector(7 downto 0));
  end D_FF;

 architecture behavioral of D_FF is
 -- signals declaration
 signal s1,s2,s3,s4,s5,s6,s7,s8: std_logic;
 begin

 --transfer the 4 bit to another register
s1 <= D(0) and (not s);
Q(0) <= s and D(0);
s2 <= D(1) and (not s);
Q(1) <= (Q(0)and s) or s2;
s3 <= D(2) and (not s);
Q(2) <= (Q(1)and s) or s3;
s4 <= D(3) and not s;
Q(3) <= (Q(2)and s)or s4;
s5 <= D(4) and not s;
Q(4) <= (Q(3)and s)or s5;
s6 <= D(5) and not s;
Q(5) <= (Q(4)and s)or s6;
s7 <= D(6) and not s;
Q(6) <= (Q(5)and s)or s7;
s8 <= D(7) and not s;
Q(7) <= (Q(6)and s)or s8;

end behavioral;

 ------------------------------
-- testbench
 ------------------------------
 -- library
library ieee;
use ieee. std_logic_1164.all;


entity testbench is 
-- empty entity
end testbench;
-----------------------------
architecture tb of testbench is -- testbench 
-- architecture  -- REDUNDANT transcription error?
 -- component declaration
 component D_FF is
 PORT( D : in std_logic_vector(7 downto 0);
       s :in std_logic;
       CLOCK: in std_logic;
       Q: out std_logic_vector(7 downto 0));
  end component;

  -- signals that need in testbench -- COMMENT DELIMITER transcription error?
  signal D_s: std_logic_vector(7 downto 0);-- signals for entity i/o
  signal Q_s: std_logic_vector(7 downto 0);-- signals for entity i/o
  signal s_s: std_logic;
  signal CLOCK_s: std_logic;
  -- is the signal that must be run 4 time to transfer the bit 
  signal loop_count: integer;
   begin

  dut:D_FF port map(D_s,Q_s,s_s,CLOCK_s);   
  -- design under test instantiation

 stimProcess: process                                           -- 
 --stimulus generator
  begin
    --the run 4 time this to transfer the 4 bit 
    for loop_counter in 0 to 3 loop
    D_s <= "01100000";
    wait until CLOCK_s = '1' and CLOCK_s'event;
    end loop;

  end process stimProcess;                                  
  -- without sensitivity list
  end tb;

Answer 1

You are using a positional association for the port map. When you do this, the order of ports in your port map must match the order of ports in your component declaration. Using positional association, the proper order is:

dut:D_FF port map(D_s,s_s,CLOCK_s,Q_s); 

Note that in your example, you've connected the signal Q_s to s , s_s to CLOCK , and CLOCK_s to Q (because your order was not the same).

I always prefer named association. On the left, you have your "formal" (the port outlined in your component declaration). On the right, you have the "actual" (the signal you're connecting to that port). The whitespace is just to improve readability.

dut: D_FF 
  port map (
    D     => D_s,
    s     => s_s,
    CLOCK => CLOCK_s,
    Q     => Q_s
  );

Named association port maps are much easier to debug, and the ports can be mapped in any order.