onescomplementadder.onescomplementadder_arc Architecture Reference

Carry Look-Ahead Full-Adder. More...

Inheritance diagram for onescomplementadder.onescomplementadder_arc:

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Collaboration diagram for onescomplementadder.onescomplementadder_arc:

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List of all members.

Processes
PROCESS_325	( CLK )
	main adder logic
Signals
propagate	std_logic_vector ( 15 downto 0 ) := ( others = > ' 0 ' )
gen_carry	std_logic_vector ( 15 downto 0 ) := ( others = > ' 0 ' )
result	std_logic_vector ( 15 downto 0 ) := ( others = > ' 0 ' )
carry	std_logic_vector ( 15 downto 0 ) := ( others = > ' 0 ' )
carry_in	std_logic := ' 0 '

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Detailed Description

Carry Look-Ahead Full-Adder.

Definition at line 53 of file onescomplementadder.vhd.

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Member Function Documentation

[Process]

PROCESS_325

( clk )

main adder logic

Definition at line 73 of file onescomplementadder.vhd.

  process(clk)
    variable x : std_logic := '0';
  begin
    if clk'event and clk = '1' then
      if RESET = '1' then
        result <= (others => '0');
        carry  <= (others => '0');
      else
        if EN = '1' then
          if C_IN = '1' then
            result(0) <= A(0) xnor B(0);
            carry(0)  <= A (0) or B(0);
          else
            result(0) <= A(0) xor B(0);
            carry(0)  <= A(0) and B(0);
          end if;
          for i in 15 downto 1 loop
            if gen_carry(i-1) = '1' then
              result(i) <= A(i) xnor B(i);
              carry(i)  <= A(i) or B(i);
            elsif propagate(i-1) = '1' then
              for j in (i-1) downto 0 loop
                if gen_carry(j) = '1' then
                  x := '1';
                  exit;
                elsif propagate(j) = '0' then
                  x := '0';
                  exit;
                else
                  x := '0';
                end if;
              end loop;
              result(i) <= (A(i) xor B(i)) xor x;
              carry(i)  <= (A(i) and B(i)) or (A(i) and x) or (B(i) and x);
            else
              result(i) <= A(i) xor B(i);
              carry(i)  <= A(i) and B(i);
            end if;
          end loop;
        end if;
      end if;
    end if;
  end process;

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The documentation for this class was generated from the following file:

• onescomplementadder.vhd