Line 1... |
Line 1... |
-- #################################################################################################
|
-- #################################################################################################
|
-- # << NEORV32 - CPU Data Register File >> #
|
-- # << NEORV32 - CPU Data Register File >> #
|
-- # ********************************************************************************************* #
|
-- # ********************************************************************************************* #
|
-- # General purpose data register file. 32 entries for normal mode (I), 16 entries for embedded #
|
-- # General purpose data register file. 32 entries for normal mode (I), 16 entries for embedded #
|
-- # mode (E) when RISC-V "E" extension is enabled. Register zero (r0) is a normal physical #
|
-- # mode (E) when RISC-V "E" extension is enabled. Register zero (r0) is a "normal" physical reg #
|
-- # registers, that has to be initialized to zero by the CPU control system. For normal #
|
-- # that has to be initialized to zero by the CPU control system. For normal operations r0 cannot #
|
-- # operations r0 cannot be written. The register file uses synchronous reads. Hence it can be #
|
-- # be written. The register file uses synchronous reads so it can be mapped to FPGA block RAM. #
|
-- # mapped to FPGA block RAM. #
|
|
-- # ********************************************************************************************* #
|
-- # ********************************************************************************************* #
|
-- # BSD 3-Clause License #
|
-- # BSD 3-Clause License #
|
-- # #
|
-- # #
|
-- # Copyright (c) 2020, Stephan Nolting. All rights reserved. #
|
-- # Copyright (c) 2020, Stephan Nolting. All rights reserved. #
|
-- # #
|
-- # #
|
Line 55... |
Line 54... |
ctrl_i : in std_ulogic_vector(ctrl_width_c-1 downto 0); -- main control bus
|
ctrl_i : in std_ulogic_vector(ctrl_width_c-1 downto 0); -- main control bus
|
-- data input --
|
-- data input --
|
mem_i : in std_ulogic_vector(data_width_c-1 downto 0); -- memory read data
|
mem_i : in std_ulogic_vector(data_width_c-1 downto 0); -- memory read data
|
alu_i : in std_ulogic_vector(data_width_c-1 downto 0); -- ALU result
|
alu_i : in std_ulogic_vector(data_width_c-1 downto 0); -- ALU result
|
csr_i : in std_ulogic_vector(data_width_c-1 downto 0); -- CSR read data
|
csr_i : in std_ulogic_vector(data_width_c-1 downto 0); -- CSR read data
|
pc_i : in std_ulogic_vector(data_width_c-1 downto 0); -- current pc
|
|
-- data output --
|
-- data output --
|
rs1_o : out std_ulogic_vector(data_width_c-1 downto 0); -- operand 1
|
rs1_o : out std_ulogic_vector(data_width_c-1 downto 0); -- operand 1
|
rs2_o : out std_ulogic_vector(data_width_c-1 downto 0) -- operand 2
|
rs2_o : out std_ulogic_vector(data_width_c-1 downto 0) -- operand 2
|
);
|
);
|
end neorv32_cpu_regfile;
|
end neorv32_cpu_regfile;
|
Line 69... |
Line 67... |
-- register file --
|
-- register file --
|
type reg_file_t is array (31 downto 0) of std_ulogic_vector(data_width_c-1 downto 0);
|
type reg_file_t is array (31 downto 0) of std_ulogic_vector(data_width_c-1 downto 0);
|
type reg_file_emb_t is array (15 downto 0) of std_ulogic_vector(data_width_c-1 downto 0);
|
type reg_file_emb_t is array (15 downto 0) of std_ulogic_vector(data_width_c-1 downto 0);
|
signal reg_file : reg_file_t;
|
signal reg_file : reg_file_t;
|
signal reg_file_emb : reg_file_emb_t;
|
signal reg_file_emb : reg_file_emb_t;
|
|
signal rf_mux_data : std_ulogic_vector(data_width_c-1 downto 0);
|
signal rf_write_data : std_ulogic_vector(data_width_c-1 downto 0); -- actual write-back data
|
signal rf_write_data : std_ulogic_vector(data_width_c-1 downto 0); -- actual write-back data
|
signal rd_is_r0 : std_ulogic; -- writing to r0?
|
signal rd_is_r0 : std_ulogic; -- writing to r0?
|
signal rf_we : std_ulogic;
|
signal rf_we : std_ulogic;
|
signal dst_addr : std_ulogic_vector(4 downto 0); -- destination address
|
signal dst_addr : std_ulogic_vector(4 downto 0); -- destination address
|
|
|
begin
|
begin
|
|
|
-- Input mux ------------------------------------------------------------------------------
|
|
-- -------------------------------------------------------------------------------------------
|
|
input_mux: process(ctrl_i, mem_i, alu_i, pc_i, csr_i)
|
|
begin
|
|
case ctrl_i(ctrl_rf_in_mux_msb_c downto ctrl_rf_in_mux_lsb_c) is
|
|
when "00" => rf_write_data <= alu_i;
|
|
when "01" => rf_write_data <= mem_i;
|
|
when "10" => rf_write_data <= pc_i;
|
|
when others => rf_write_data <= csr_i;
|
|
end case;
|
|
end process input_mux;
|
|
|
|
-- check if we are writing to x0 --
|
|
rd_is_r0 <= not or_all_f(ctrl_i(ctrl_rf_rd_adr4_c downto ctrl_rf_rd_adr0_c)) when (CPU_EXTENSION_RISCV_E = false) else
|
|
not or_all_f(ctrl_i(ctrl_rf_rd_adr3_c downto ctrl_rf_rd_adr0_c));
|
|
|
|
-- valid RF write access --
|
|
rf_we <= (ctrl_i(ctrl_rf_wb_en_c) and (not rd_is_r0)) or ctrl_i(ctrl_rf_r0_we_c);
|
|
|
|
-- destination address --
|
|
dst_addr <= ctrl_i(ctrl_rf_rd_adr4_c downto ctrl_rf_rd_adr0_c) when (ctrl_i(ctrl_rf_r0_we_c) = '0') else (others => '0'); -- force dst=r0?
|
|
|
|
|
|
-- Register file read/write access --------------------------------------------------------
|
-- Register file read/write access --------------------------------------------------------
|
-- -------------------------------------------------------------------------------------------
|
-- -------------------------------------------------------------------------------------------
|
rf_access: process(clk_i)
|
rf_access: process(clk_i)
|
begin
|
begin
|
if rising_edge(clk_i) then -- sync read and write
|
if rising_edge(clk_i) then -- sync read and write
|
if (CPU_EXTENSION_RISCV_E = false) then -- normal register file with 32 entries
|
if (CPU_EXTENSION_RISCV_E = false) then -- normal register file with 32 entries
|
if (rf_we = '1') then
|
if (rf_we = '1') then
|
reg_file(to_integer(unsigned(dst_addr(4 downto 0)))) <= rf_write_data;
|
reg_file(to_integer(unsigned(dst_addr(4 downto 0)))) <= rf_write_data;
|
else -- read
|
else
|
rs1_o <= reg_file(to_integer(unsigned(ctrl_i(ctrl_rf_rs1_adr4_c downto ctrl_rf_rs1_adr0_c))));
|
rs1_o <= reg_file(to_integer(unsigned(ctrl_i(ctrl_rf_rs1_adr4_c downto ctrl_rf_rs1_adr0_c))));
|
rs2_o <= reg_file(to_integer(unsigned(ctrl_i(ctrl_rf_rs2_adr4_c downto ctrl_rf_rs2_adr0_c))));
|
rs2_o <= reg_file(to_integer(unsigned(ctrl_i(ctrl_rf_rs2_adr4_c downto ctrl_rf_rs2_adr0_c))));
|
end if;
|
end if;
|
else -- embedded register file with 16 entries
|
else -- embedded register file with 16 entries
|
if (rf_we = '1') then
|
if (rf_we = '1') then
|
reg_file_emb(to_integer(unsigned(dst_addr(3 downto 0)))) <= rf_write_data;
|
reg_file_emb(to_integer(unsigned(dst_addr(3 downto 0)))) <= rf_write_data;
|
else -- read
|
else
|
rs1_o <= reg_file_emb(to_integer(unsigned(ctrl_i(ctrl_rf_rs1_adr3_c downto ctrl_rf_rs1_adr0_c))));
|
rs1_o <= reg_file_emb(to_integer(unsigned(ctrl_i(ctrl_rf_rs1_adr3_c downto ctrl_rf_rs1_adr0_c))));
|
rs2_o <= reg_file_emb(to_integer(unsigned(ctrl_i(ctrl_rf_rs2_adr3_c downto ctrl_rf_rs2_adr0_c))));
|
rs2_o <= reg_file_emb(to_integer(unsigned(ctrl_i(ctrl_rf_rs2_adr3_c downto ctrl_rf_rs2_adr0_c))));
|
end if;
|
end if;
|
end if;
|
end if;
|
end if;
|
end if;
|
end process rf_access;
|
end process rf_access;
|
|
|
|
-- data input mux --
|
|
rf_write_data <= alu_i when (ctrl_i(ctrl_rf_in_mux_msb_c) = '0') else rf_mux_data;
|
|
rf_mux_data <= mem_i when (ctrl_i(ctrl_rf_in_mux_lsb_c) = '0') else csr_i;
|
|
|
|
-- check if we are writing to x0 --
|
|
rd_is_r0 <= not or_all_f(ctrl_i(ctrl_rf_rd_adr4_c downto ctrl_rf_rd_adr0_c)) when (CPU_EXTENSION_RISCV_E = false) else
|
|
not or_all_f(ctrl_i(ctrl_rf_rd_adr3_c downto ctrl_rf_rd_adr0_c));
|
|
|
|
-- valid RF write access --
|
|
rf_we <= (ctrl_i(ctrl_rf_wb_en_c) and (not rd_is_r0)) or ctrl_i(ctrl_rf_r0_we_c);
|
|
|
|
-- destination address --
|
|
dst_addr <= ctrl_i(ctrl_rf_rd_adr4_c downto ctrl_rf_rd_adr0_c) when (ctrl_i(ctrl_rf_r0_we_c) = '0') else (others => '0'); -- force dst=r0?
|
|
|
|
|
|
|
end neorv32_cpu_regfile_rtl;
|
end neorv32_cpu_regfile_rtl;
|
|
|
No newline at end of file
|
No newline at end of file
|