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yapzihe |
----------------------------------------------------------------------------
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---- ----
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---- WISHBONE RISCMCU IP Core ----
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---- ----
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---- This file is part of the RISCMCU project ----
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---- http://www.opencores.org/projects/riscmcu/ ----
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---- ----
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---- Description ----
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---- Implementation of a RISC Microcontroller based on Atmel AVR ----
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---- AT90S1200 instruction set and features with Altera Flex10k20 FPGA. ----
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---- ----
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---- Author(s): ----
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---- - Yap Zi He, yapzihe@hotmail.com ----
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---- ----
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----------------------------------------------------------------------------
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---- ----
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---- Copyright (C) 2001 Authors and OPENCORES.ORG ----
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---- ----
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---- This source file may be used and distributed without ----
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---- restriction provided that this copyright statement is not ----
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---- removed from the file and that any derivative work contains ----
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---- the original copyright notice and the associated disclaimer. ----
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---- ----
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---- This source file is free software; you can redistribute it ----
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---- and/or modify it under the terms of the GNU Lesser General ----
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---- Public License as published by the Free Software Foundation; ----
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---- either version 2.1 of the License, or (at your option) any ----
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---- later version. ----
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---- ----
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---- This source is distributed in the hope that it will be ----
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---- useful, but WITHOUT ANY WARRANTY; without even the implied ----
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---- warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ----
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---- PURPOSE. See the GNU Lesser General Public License for more ----
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---- details. ----
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---- ----
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---- You should have received a copy of the GNU Lesser General ----
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---- Public License along with this source; if not, download it ----
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---- from http://www.opencores.org/lgpl.shtml ----
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---- ----
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----------------------------------------------------------------------------
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library ieee;
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use ieee.std_logic_1164.all;
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use ieee.std_logic_unsigned.all;
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entity v_pc is
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port( offset : in std_logic_vector(8 downto 0);
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en, addoffset, push, pull, vec2, vec4 : in std_logic;
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clk, clrn : in std_logic;
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pc : buffer std_logic_vector(8 downto 0)
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);
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end v_pc;
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architecture pc of v_pc is
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constant vector2 : std_logic_vector(8 downto 0) := "000000001";
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constant vector4 : std_logic_vector(8 downto 0) := "000000010";
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signal pcb, stack0, stack1, stack2, stack3 : std_logic_vector(8 downto 0);
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begin
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process(clk, clrn)
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begin
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if clrn = '0' then
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pc <= "000000000";
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pcb <= "000000000";
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stack0 <= "000000000";
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stack1 <= "000000000";
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stack2 <= "000000000";
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stack3 <= "000000000";
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elsif clk'event and clk = '1' then
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if en = '1' then
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pcb <= pc;
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if addoffset = '1' then
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pc <= pcb + offset;
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elsif pull = '1' then
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pc <= stack0;
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elsif vec2 = '1' then
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pc <= vector2;
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elsif vec4 = '1' then
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pc <= vector4;
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else
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pc <= pc + 1;
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end if;
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if push = '1' then
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if addoffset = '1' then
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stack0 <= pcb;
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else
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stack0 <= pcb - 1;
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end if;
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stack1 <= stack0;
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stack2 <= stack1;
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stack3 <= stack2;
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elsif pull = '1' then
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stack0 <= stack1;
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stack1 <= stack2;
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stack2 <= stack3;
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end if;
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end if;
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end if;
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end process;
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end pc;
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