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-------------------------------------------------------------------------------
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-------------------------------------------------------------------------------
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--
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--
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-- The Clock Control unit.
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-- The Clock Control unit.
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-- Clock States and Machine Cycles are generated here.
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-- Clock States and Machine Cycles are generated here.
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--
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--
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-- $Id: clock_ctrl.vhd,v 1.2 2004-03-28 12:55:06 arniml Exp $
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-- $Id: clock_ctrl.vhd,v 1.3 2004-04-18 18:56:23 arniml Exp $
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--
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--
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-- Copyright (c) 2004, Arnim Laeuger (arniml@opencores.org)
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-- Copyright (c) 2004, Arnim Laeuger (arniml@opencores.org)
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--
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--
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-- All rights reserved
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-- All rights reserved
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--
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--
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-- The Clock State controller.
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-- The Clock State controller.
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--
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--
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states: process (res_i, clk_i)
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states: process (res_i, clk_i)
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begin
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begin
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if res_i = res_active_c then
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if res_i = res_active_c then
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mstate_q <= MSTATE1;
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-- Reset machine state to MSTATE3
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-- This allows a proper instruction fetch for the first real instruction
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-- after reset.
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-- The MSTATE3 is part of a virtual NOP that has no MSTATE1 and MSTATE2.
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mstate_q <= MSTATE3;
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elsif clk_i'event and clk_i = clk_active_c then
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elsif clk_i'event and clk_i = clk_active_c then
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if en_clk_i then
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if en_clk_i then
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case mstate_q is
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case mstate_q is
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second_cycle_q <= true;
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second_cycle_q <= true;
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end if;
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end if;
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-- reset at end of second machine cycle
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-- reset at end of second machine cycle
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if state5_v and
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if state5_v and
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(not multi_cycle_q or
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(multi_cycle_q and second_cycle_q) then
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(multi_cycle_q and second_cycle_q)) then
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multi_cycle_q <= false;
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multi_cycle_q <= false;
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second_cycle_q <= false;
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second_cycle_q <= false;
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end if;
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end if;
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end if;
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end if;
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-------------------------------------------------------------------------------
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-------------------------------------------------------------------------------
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-- File History:
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-- File History:
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--
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--
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-- $Log: not supported by cvs2svn $
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-- $Log: not supported by cvs2svn $
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-- Revision 1.2 2004/03/28 12:55:06 arniml
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-- move code for PROG out of if-branch for xtal3_s
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--
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-- Revision 1.1 2004/03/23 21:31:52 arniml
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-- Revision 1.1 2004/03/23 21:31:52 arniml
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-- initial check-in
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-- initial check-in
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--
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--
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--
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--
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-------------------------------------------------------------------------------
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-------------------------------------------------------------------------------
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