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You can instantiate Altera-provided logic functions from the alt_mf library, which includes the a_8fadd, a_8mcomp, a_8count, and a_81mux functions, in VHDL designs. Altera^® provides behavioral descriptions of these functions that support prerouting simulation of your top-level design with the VHDL System Simulator (VSS).

When you instantiate one of these functions, you can either include a Component Declaration for the function, or use the Altera-provided shell script analyze_vss to create a design library called altera so that you can reference the functions through the VHDL Library and Use Clauses. The Library and Use Clauses direct the Design Compiler to incorporate the library files when it compiles your top-level design file. The

The following example shows an 8-bit counter that is instantiated using the a_8count function.

Sample VHDL File with Logic Function Instantiation

LIBRARY ieee;
USE ieee.std_logic_1164.ALL;

LIBRARY altera;
USE altera.quartus.ALL;

ENTITY counter IS
PORT (clock,ena,load,dnup,set,clear : IN STD_LOGIC;
   i    : IN STD_LOGIC_VECTOR (7 DOWNTO 0);
   q    : OUT STD_LOGIC_VECTOR(7 DOWNTO 0);

   cout : OUT STD_LOGIC);
END counter;

ARCHITECTURE structure OF counter IS

BEGIN
   u1   : a_8count

   PORT MAP (a=>i(0), b=>i(1), c=>i(2), d=>i(3), e=>i(4),
            f=>i(5), g=>i(6), h=>i(7), ldn=>load, gn=>ena, 
            dnup=>dnup, setn=>set, clrn=>clear, clk=>clock, 

            qa=>q(0), qb=>q(1), qc=>q(2), qd=>q(3), qe=>q(4), 
            qf=>q(5), qg=>q(6), qh=>q(7), cout=>cout);

END structure;

CONFIGURATION conf OF counter IS
   FOR structure
   END FOR;
END conf;

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