URL
https://opencores.org/ocsvn/potato/potato/trunk
Subversion Repositories potato
[/] [potato/] [tags/] [v0.1/] [src/] [pp_alu_control_unit.vhd] - Rev 53
Go to most recent revision | Compare with Previous | Blame | View Log
-- The Potato Processor - A simple processor for FPGAs -- (c) Kristian Klomsten Skordal 2014 - 2015 <kristian.skordal@wafflemail.net> -- Report bugs and issues on <http://opencores.org/project,potato,bugtracker> library ieee; use ieee.std_logic_1164.all; use work.pp_types.all; use work.pp_constants.all; entity pp_alu_control_unit is port( opcode : in std_logic_vector( 4 downto 0); funct3 : in std_logic_vector( 2 downto 0); funct7 : in std_logic_vector( 6 downto 0); -- Sources of ALU operands: alu_x_src, alu_y_src : out alu_operand_source; -- ALU operation: alu_op : out alu_operation ); end entity pp_alu_control_unit; architecture behaviour of pp_alu_control_unit is begin decode_alu: process(opcode, funct3, funct7) begin case opcode is when b"01101" => -- Load upper immediate alu_x_src <= ALU_SRC_NULL; alu_y_src <= ALU_SRC_IMM; alu_op <= ALU_ADD; when b"00101" => -- Add upper immediate to PC alu_x_src <= ALU_SRC_PC; alu_y_src <= ALU_SRC_IMM; alu_op <= ALU_ADD; when b"11011" => -- Jump and link alu_x_src <= ALU_SRC_PC_NEXT; alu_y_src <= ALU_SRC_NULL; alu_op <= ALU_ADD; when b"11001" => -- Jump and link register alu_x_src <= ALU_SRC_PC_NEXT; alu_y_src <= ALU_SRC_NULL; alu_op <= ALU_ADD; when b"11000" => -- Branch operations -- The funct3 field decides which type of branch comparison is -- done; this is decoded in the branch comparator module. alu_x_src <= ALU_SRC_NULL; alu_y_src <= ALU_SRC_NULL; alu_op <= ALU_NOP; when b"00000" => -- Load instruction alu_x_src <= ALU_SRC_REG; alu_y_src <= ALU_SRC_IMM; alu_op <= ALU_ADD; when b"01000" => -- Store instruction alu_x_src <= ALU_SRC_REG; alu_y_src <= ALU_SRC_IMM; alu_op <= ALU_ADD; when b"00100" => -- Register-immediate operations alu_x_src <= ALU_SRC_REG; if funct3 = b"001" or funct3 = b"101" then alu_y_src <= ALU_SRC_SHAMT; else alu_y_src <= ALU_SRC_IMM; end if; case funct3 is when b"000" => alu_op <= ALU_ADD; when b"001" => alu_op <= ALU_SLL; when b"010" => alu_op <= ALU_SLT; when b"011" => alu_op <= ALU_SLTU; when b"100" => alu_op <= ALU_XOR; when b"101" => if funct7 = b"0000000" then alu_op <= ALU_SRL; else alu_op <= ALU_SRA; end if; when b"110" => alu_op <= ALU_OR; when b"111" => alu_op <= ALU_AND; when others => alu_op <= ALU_INVALID; end case; when b"01100" => -- Register-register operations alu_x_src <= ALU_SRC_REG; alu_y_src <= ALU_SRC_REG; case funct3 is when b"000" => if funct7 = b"0000000" then alu_op <= ALU_ADD; else alu_op <= ALU_SUB; end if; when b"001" => alu_op <= ALU_SLL; when b"010" => alu_op <= ALU_SLT; when b"011" => alu_op <= ALU_SLTU; when b"100" => alu_op <= ALU_XOR; when b"101" => if funct7 = b"0000000" then alu_op <= ALU_SRL; else alu_op <= ALU_SRA; end if; when b"110" => alu_op <= ALU_OR; when b"111" => alu_op <= ALU_AND; when others => alu_op <= ALU_INVALID; end case; when b"00011" => -- Fence instructions, ignored alu_x_src <= ALU_SRC_REG; alu_y_src <= ALU_SRC_REG; alu_op <= ALU_NOP; when b"11100" => -- System instructions alu_x_src <= ALU_SRC_CSR; alu_y_src <= ALU_SRC_NULL; alu_op <= ALU_ADD; when others => alu_x_src <= ALU_SRC_REG; alu_y_src <= ALU_SRC_REG; alu_op <= ALU_INVALID; end case; end process decode_alu; end architecture behaviour;
Go to most recent revision | Compare with Previous | Blame | View Log