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Line 21... |
c_alu : out std_logic_vector(31 downto 0));
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c_alu : out std_logic_vector(31 downto 0));
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end; --alu
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end; --alu
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architecture logic of alu is
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architecture logic of alu is
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-- type alu_function_type is (alu_nothing, alu_add, alu_subtract,
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-- type alu_function_type is (alu_nothing, alu_add, alu_subtract,
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-- alu_less_than, alu_less_than_signed, alu_equal, alu_not_equal,
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-- alu_less_than, alu_less_than_signed,
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-- alu_ltz, alu_lez, alu_eqz, alu_nez, alu_gez, alu_gtz,
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-- alu_or, alu_and, alu_xor, alu_nor);
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-- alu_or, alu_and, alu_xor, alu_nor);
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signal aa, bb, sum : std_logic_vector(32 downto 0);
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signal aa, bb, sum : std_logic_vector(32 downto 0);
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signal do_add : std_logic;
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signal do_add : std_logic;
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begin
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begin
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alu_proc: process(a_in, b_in, alu_function, sum)
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alu_proc: process(a_in, b_in, alu_function, sum)
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variable c : std_logic_vector(31 downto 0);
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variable a_eq_b : std_logic;
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variable a_zero : std_logic;
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variable sign_ext : std_logic;
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variable sign_ext : std_logic;
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begin
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begin
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c := ZERO;
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if alu_function = alu_add then
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if alu_function = alu_add then
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do_add <= '1';
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do_add <= '1';
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else
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else
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do_add <= '0';
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do_add <= '0';
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end if;
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end if;
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sign_ext := '1';
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sign_ext := '1';
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end if;
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end if;
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aa <= (a_in(31) and sign_ext) & a_in;
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aa <= (a_in(31) and sign_ext) & a_in;
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bb <= (b_in(31) and sign_ext) & b_in;
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bb <= (b_in(31) and sign_ext) & b_in;
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-- Choose bv_adder or lpm_add_sub
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-- sum <= bv_adder(aa, bb, do_add);
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-- sum <= bv_adder_lookahead(aa, bb, do_add);
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if a_in = b_in then
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a_eq_b := '1';
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else
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a_eq_b := '0';
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end if;
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if a_in = ZERO then
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a_zero := '1';
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else
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a_zero := '0';
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end if;
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case alu_function is
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case alu_function is
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when alu_add | alu_subtract => --c=a+b
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when alu_add | alu_subtract => --c=a+b
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c := sum(31 downto 0);
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c_alu <= sum(31 downto 0);
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when alu_less_than => --c=a<b
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when alu_less_than => --c=a<b
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c(0) := sum(32);
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c_alu <= ZERO(31 downto 1) & sum(32);
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when alu_less_than_signed => --c=a<b;
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when alu_less_than_signed => --c=a<b;
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c(0) := sum(32);
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c_alu <= ZERO(31 downto 1) & sum(32);
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when alu_equal => --c=a==b
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c(0) := a_eq_b;
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when alu_not_equal => --c=a!=b
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c(0) := not a_eq_b;
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when alu_ltz => --c=a<0
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c(0) := a_in(31);
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when alu_lez => --c=a<=0
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c(0) := a_in(31) or a_zero;
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when alu_eqz => --c=a==0
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c(0) := a_zero;
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when alu_nez => --c=a!=0
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c(0) := not a_zero;
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when alu_gez => --c=a>=0
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c(0) := not a_in(31);
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when alu_gtz => --c=a>0
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c(0) := not a_zero and not a_in(31);
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when alu_or => --c=a|b
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when alu_or => --c=a|b
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c := a_in or b_in;
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c_alu <= a_in or b_in;
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when alu_and => --c=a&b
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when alu_and => --c=a&b
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c := a_in and b_in;
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c_alu <= a_in and b_in;
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when alu_xor => --c=a^b
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when alu_xor => --c=a^b
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c := a_in xor b_in;
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c_alu <= a_in xor b_in;
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when alu_nor => --c=~(a|b)
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when alu_nor => --c=~(a|b)
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c := a_in nor b_in;
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c_alu <= a_in nor b_in;
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when others => --alu_function = alu_nothing
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when others => --alu_function = alu_nothing
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c := ZERO;
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c_alu <= ZERO;
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end case;
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end case;
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c_alu <= c;
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end process;
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end process;
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generic_adder:
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generic_adder:
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if adder_type /= "ALTERA" generate
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if adder_type /= "ALTERA" generate
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