LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.numeric_std.all;
USE work.mips_types.all;
ENTITY e_mips_regs IS
PORT (
clk: IN std_logic;
i_rd_a_no: IN std_logic_vector( 4 DOWNTO 0);
o_rd_a_data: OUT std_logic_vector(31 DOWNTO 0);
i_rd_b_no: IN std_logic_vector( 4 DOWNTO 0);
o_rd_b_data: OUT std_logic_vector(31 DOWNTO 0);
i_wr_no: IN std_logic_vector( 4 DOWNTO 0);
i_wr_data: IN std_logic_vector(31 DOWNTO 0);
i_wr_en: IN std_logic
);
END ENTITY e_mips_regs;
ARCHITECTURE a_mips_regs OF e_mips_regs IS
SUBTYPE t_idx IS natural RANGE 31 DOWNTO 0;
TYPE t_regs IS ARRAY(t_idx) OF std_logic_vector(31 DOWNTO 0);
SIGNAL r_regs: t_regs := (OTHERS => (OTHERS => '0'));
FUNCTION no2idx(no: std_logic_vector(4 DOWNTO 0)) RETURN natural IS
BEGIN
RETURN to_integer(unsigned(no));
END FUNCTION no2idx;
BEGIN
p_read_a: PROCESS(i_rd_a_no, r_regs)
BEGIN
IF i_rd_a_no = "00000" THEN
o_rd_a_data <= X"00000000";
ELSE
o_rd_a_data <= r_regs(no2idx(i_rd_a_no));
END IF;
END PROCESS p_read_a;
p_read_b: PROCESS(i_rd_b_no, r_regs)
BEGIN
IF i_rd_b_no = "00000" THEN
o_rd_b_data <= X"00000000";
ELSE
o_rd_b_data <= r_regs(no2idx(i_rd_b_no));
END IF;
END PROCESS p_read_b;
