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__alexs__ |
-- --------------------------------------------------------------------------
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-- >>>>>>>>>>>>>>>>>>>>>>>>>>>> COPYRIGHT NOTICE <<<<<<<<<<<<<<<<<<<<<<<<<<<<
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-- --------------------------------------------------------------------------
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-- TITLE: Plasma COMPARATOR
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-- AUTHOR: Alex Schoenberger (Alex.Schoenberger@ies.tu-darmstadt.de)
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-- COMMENT: This project is based on Plasma CPU core by Steve Rhoads
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--
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-- www.ies.tu-darmstadt.de
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-- TU Darmstadt
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-- Institute for Integrated Systems
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-- Merckstr. 25
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--
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-- 64283 Darmstadt - GERMANY
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-- --------------------------------------------------------------------------
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-- PROJECT: Plasma CPU core with FPU
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-- FILENAME: plasma_comparator.vhd
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-- --------------------------------------------------------------------------
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-- COPYRIGHT:
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-- This project is distributed by GPLv2.0
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-- Software placed into the public domain by the author.
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-- Software 'as is' without warranty. Author liable for nothing.
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-- --------------------------------------------------------------------------
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-- DESCRIPTION:
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-- compares input values depeding on operation code
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--
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-- SYNTHESIZABLE
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--
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----------------------------------------------------------------------------
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-- Revision History
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-- --------------------------------------------------------------------------
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-- Revision Date Author CHANGES
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-- 1.0 4/2014 AS initial
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-- 2.0 5/2015 AS works with MIPS I commands directly
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-- --------------------------------------------------------------------------
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library IEEE;
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use IEEE.std_logic_1164.ALL;
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library PLASMA;
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use PLASMA.mips_instruction_set.ALL;
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use PLASMA.plasma_pack.ALL;
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entity plasma_comparator is
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port(
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comp_a_in : in t_plasma_word;
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comp_b_in : in t_plasma_word;
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comp_func : in t_mips_opcode;
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comp_out : out std_logic
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);
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end entity plasma_comparator;
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architecture structure_comparator of plasma_comparator is
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alias func : std_logic_vector(2 downto 0) is comp_func(2 downto 0);
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signal comp_eq : std_logic; -- input values are equal
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signal comp_eq_z : std_logic; -- input = 0
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signal comp_neg : std_logic; -- input < 0
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begin
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comp_eq <= '1' when comp_a_in = comp_b_in else '0';
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comp_eq_z <= '1' when comp_a_in = PLASMA_ZERO_WORD else '0';
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comp_neg <= comp_a_in(PLASMA_DATA_WIDTH - 1); -- check MSB
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-- COMPARATOR MUX
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with func select
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comp_out <= comp_eq when "100", -- BEQ
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not comp_eq when "101", -- BNE
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comp_neg or comp_eq_z when "110", -- BLEZ
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not(comp_neg or comp_eq_z) when "111", -- BGTZ
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comp_neg when "000", -- BLTZ
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not comp_neg when "001", -- BGEZ
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'0' when others;
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end architecture structure_comparator;
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