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-- $Id: dcm_sfs_unisim_s3e.vhd 534 2013-09-22 21:37:24Z mueller $

--

-- Copyright 2010-2011 by Walter F.J. Mueller <W.F.J.Mueller@gsi.de>

--

-- This program is free software; you may redistribute and/or modify it under

-- the terms of the GNU General Public License as published by the Free

-- Software Foundation, either version 2, or at your option any later version.

--

-- This program is distributed in the hope that it will be useful, but

-- WITHOUT ANY WARRANTY, without even the implied warranty of MERCHANTABILITY

-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

-- for complete details.

--

------------------------------------------------------------------------------

-- Module Name:    dcm_sfs - syn

-- Description:    DCM for simple frequency synthesis; SPARTAN-3E version

--                 Direct instantiation of Xilinx UNISIM primitives

--

-- Dependencies:   -

-- Test bench:     -

-- Target Devices: generic Spartan-3A,-3E; Spartan-6

-- Tool versions:  xst 12.1; ghdl 0.29

--

-- Revision History: 

-- Date         Rev Version  Comment

-- 2011-11-17   426   1.0.3  rename dcm_sp_sfs -> dcm_sfs, SPARTAN-3E version

-- 2011-11-10   423   1.0.2  add FAMILY generic, SPARTAN-3 support

-- 2010-11-12   338   1.0.1  drop SB_CLK generic; allow DIV=1,MUL=1 without DCM

-- 2010-11-07   337   1.0    Initial version 

------------------------------------------------------------------------------

library ieee;

use ieee.std_logic_1164.all;

library unisim;

use unisim.vcomponents.ALL;

use work.slvtypes.all;

entity dcm_sfs is                       -- DCM for simple frequency synthesis

  generic (

    CLKFX_DIVIDE : positive := 1;       -- FX clock divide   (1-32)

    CLKFX_MULTIPLY : positive := 1;     -- FX clock multiply (2-32) (1->no DCM)

    CLKIN_PERIOD : real := 20.0);       -- CLKIN period (def is 20.0 ns)

  port (

    CLKIN : in slbit;                   -- clock input

    CLKFX : out slbit;                  -- clock output (synthesized freq.) 

    LOCKED : out slbit                  -- dcm locked

  );

end dcm_sfs;

architecture syn of dcm_sfs is

begin

  assert (CLKFX_DIVIDE=1 and CLKFX_MULTIPLY=1) or CLKFX_MULTIPLY>=2

  report "assert((FX_DIV=1 and FX_MULT)=1 or FX_MULT>=2"

  severity failure;

  DCM0: if CLKFX_DIVIDE=1 and CLKFX_MULTIPLY=1 generate

    CLKFX  <= CLKIN;

    LOCKED <= '1';

  end generate DCM0;

  DCM1: if CLKFX_MULTIPLY>=2 generate

    DCM : dcm_sp

      generic map (

        CLK_FEEDBACK       => "NONE",

        CLKFX_DIVIDE       => CLKFX_DIVIDE,

        CLKFX_MULTIPLY     => CLKFX_MULTIPLY,

        CLKIN_DIVIDE_BY_2  => false,

        CLKIN_PERIOD       => CLKIN_PERIOD,

        CLKOUT_PHASE_SHIFT => "NONE",

        DESKEW_ADJUST      => "SYSTEM_SYNCHRONOUS",

        DSS_MODE           => "NONE")

      port map (

        CLKIN   => CLKIN,

        CLKFX   => CLKFX,

        LOCKED  => LOCKED

      );

  end generate DCM1;

end syn;