-- MIPS I system
-- Copyright 2011-2012 Stefan Schuermans <stefan@blinkenarea.org>
-- Copyleft GNU public license V2 or later
--          http://www.gnu.org/copyleft/gpl.html

LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.numeric_std.all;

PACKAGE mips_types IS

    -- operation
    TYPE t_op IS (
        op_none,
        op_alu,   -- ALU operation
        op_div,   -- divide
        op_divu,  -- divide unsigned
        op_j,     -- jump or branch
        op_l,     -- load
        op_mfhi,  -- move from HI
        op_mflo,  -- move from LO
        op_mthi,  -- move to HI
        op_mtlo,  -- move to LO
        op_mult,  -- multiply
        op_multu, -- multiply unsigned
        op_s      -- store
    );

    -- link (store return address in register)
    TYPE t_link IS (
        link_none,
        link_link  -- link
    );

    -- compare mode
    TYPE t_cmp IS (
        cmp_none,
        cmp_eq,   -- equal
        cmp_gez,  -- greater or equal zero
        cmp_gtz,  -- greater than zero
        cmp_lez,  -- less or equal zero
        cmp_ltz,  -- less than zero
        cmp_ne    -- not equal
    );

    -- ALU operation
    TYPE t_alu IS (
        alu_none,
        alu_add,  -- addition
        alu_and,  -- bitwise AND
        alu_nor,  -- bitwise NOR
        alu_or,   -- bitwise OR
        alu_sub,  -- subtraction
        alu_sll,  -- shift left logically
        alu_sra,  -- shift right arithmetically
        alu_srl,  -- shift right logically
        alu_slt,  -- set on less than
        alu_sltu, -- set on less than unsigned
        alu_up,   -- move to upper half
        alu_xor   -- bitwise XOR
    );

    -- immediate usage
    TYPE t_imm IS (
        imm_none,
        imm_a,    -- "a" immediate
        imm_16se, -- 16 bit immediate, sign-extension
        imm_16ze, -- 16 bit immediate, zero-extension
        imm_26    -- 26 bit immediate
    );

    -- load/store type
    TYPE t_ldst IS (
        ldst_none,
        ldst_b,  -- byte (sign-extension)
        ldst_bu, -- byte unsigned (zero-extension)
        ldst_h,  -- half word (16 bit) (sign-extension)
        ldst_hu, -- half word unsigned (16 bit) (zero-extension)
        ldst_w,  -- word (32 bit)
        ldst_wl, -- word left (8 to 32 bits)
        ldst_wr  -- word right (8 to 32 bits)
    );

END PACKAGE;