01-28-2012 08:03 AM
hiI am a new to VHDL and currently doing VHDL assignment. In this assignment, required to create the D, JK flip-flop. I need help to solve my error for my code as shown as below: library ieee; use ieee.std_logic_1164.all; library work; entity Lab1 is port ( J :in std_logic; K :in std_logic; clk :in std_logic; Q : out std_logic; qn :out std_logic ); end Lab1; architecture arc of Lab1 is signal W1 : std_logic; signal W2 : std_logic; signal W3 : std_logic; signal W4 : std_logic; signal W5 : std_logic; signal W6 : std_logic; begin qn <= W4; W1 <= not (J and clk and W4); W2 <= not (K and clk and W3); W3 <= W1 nand W4; W4 <= W2 nand W3; process(clk) begin if rising_edge(clk)then Q <=(J and (not Q)) or ((not K) and Q); qn <=not Q ; end if; end process; end arc; ------------------------------------------ Error (10309): VHDL Interface Declaration error in Lab1.vhd(41): interface object "Q" of mode out cannot be read. Change object mode to buffer. Pls help me to solve the syntax error Thanks
01-28-2012 09:11 AM
Two options:- change Q from out to buffer - use an internal signal Qi and copy it to Q outside the edge sensitive condition. Also the assignment for qn must be placed outside the rising_edge() condition, otherwise it's delayed by one clock.
01-29-2012 08:24 AM
--- Quote Start --- BTW, shouldn't qn <= not Qi; Q <= Qi be outside the process? --- Quote End --- Yes, they must for correct simulation, or Qi needs to be added to the sensitive list. Thanks!