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[/] [open8_urisc/] [trunk/] [VHDL/] [o8_clk_detect.vhd] - Rev 244
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-- Copyright (c)2013, 2020 Jeremy Seth Henry -- All rights reserved. -- -- Redistribution and use in source and binary forms, with or without -- modification, are permitted provided that the following conditions are met: -- * Redistributions of source code must retain the above copyright -- notice, this list of conditions and the following disclaimer. -- * Redistributions in binary form must reproduce the above copyright -- notice, this list of conditions and the following disclaimer in the -- documentation and/or other materials provided with the distribution, -- where applicable (as part of a user interface, debugging port, etc.) -- -- THIS SOFTWARE IS PROVIDED BY JEREMY SETH HENRY ``AS IS'' AND ANY -- EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED -- WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE -- DISCLAIMED. IN NO EVENT SHALL JEREMY SETH HENRY BE LIABLE FOR ANY -- DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES -- (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; -- LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND -- ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT -- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF -- THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. -- -- VHDL Units : o8_clk_detect -- Description: Provides up/down status and interrupt for monitoring a clock -- -- Register Map: -- Offset Bitfield Description Read/Write -- 0x00 BA------ Recieve Clock Status (RO) -- A = Clock Line State (follows input) -- B = Clock Detect (1 = transition detected) -- -- Revision History -- Author Date Change ------------------ -------- --------------------------------------------------- -- Seth Henry 04/16/20 Revision block added library ieee; use ieee.std_logic_1164.all; use ieee.std_logic_unsigned.all; use ieee.std_logic_arith.all; use ieee.std_logic_misc.all; library work; use work.open8_pkg.all; entity o8_clk_detect is generic( Threshold_Count : integer; Address : ADDRESS_TYPE ); port( Ref_Clk_In : in std_logic; -- Open8_Bus : in OPEN8_BUS_TYPE; Rd_Data : out DATA_TYPE; Interrupt : out std_logic ); end entity; architecture behave of o8_clk_detect is alias Clock is Open8_Bus.Clock; alias Reset is Open8_Bus.Reset; constant User_Addr : std_logic_vector(15 downto 0) := Address; alias Comp_Addr is Open8_Bus.Address(15 downto 0); signal Addr_Match : std_logic := '0'; signal Rd_En_d : std_logic := '0'; signal Rd_En_q : std_logic := '0'; constant Threshold_bits : integer := ceil_log2(Threshold_Count); constant THRESHOLD : std_logic_vector(Threshold_bits - 1 downto 0) := conv_std_logic_vector(Threshold_Count,Threshold_bits); signal RE_Threshold_Ctr : std_logic_vector(Threshold_Bits - 1 downto 0) := (others => '0'); signal FE_Threshold_Ctr : std_logic_vector(Threshold_Bits - 1 downto 0) := (others => '0'); signal Ref_In_SR : std_logic_vector(3 downto 0) := (others => '0'); alias Ref_In_q1 is Ref_In_SR(2); alias Ref_In_q2 is Ref_In_SR(3); signal Ref_In_RE : std_logic := '0'; signal Ref_In_FE : std_logic := '0'; signal Ref_Detect : std_logic := '0'; signal Ref_Detect_q1 : std_logic := '0'; signal Ref_Detect_CoS : std_logic := '0'; begin Addr_Match <= '1' when Comp_Addr = User_Addr else '0'; Rd_En_d <= Addr_Match and Open8_Bus.Rd_En; io_reg: process( Clock, Reset ) begin if( Reset = Reset_Level )then Rd_En_q <= '0'; Rd_Data <= OPEN8_NULLBUS; elsif( rising_edge( Clock ) )then Rd_En_q <= Rd_En_d; Rd_Data <= OPEN8_NULLBUS; if( Rd_En_q = '1' )then Rd_Data(6) <= Ref_In_q2; Rd_Data(7) <= Ref_Detect; end if; end if; end process; Detect_proc: process( Clock, Reset ) begin if( Reset = Reset_Level )then Ref_In_SR <= (others => '0'); Ref_In_RE <= '0'; Ref_In_FE <= '0'; RE_Threshold_Ctr <= (others => '0'); FE_Threshold_Ctr <= (others => '0'); Ref_Detect <= '0'; Interrupt <= '0'; elsif( rising_edge(Clock) )then Ref_In_SR <= Ref_In_SR(2 downto 0) & Ref_Clk_In; Ref_In_RE <= Ref_In_q1 and (not Ref_In_q2); Ref_In_FE <= (not Ref_In_q1) and Ref_In_q2; RE_Threshold_Ctr <= RE_Threshold_Ctr - 1; if( Ref_In_RE = '1' )then RE_Threshold_Ctr <= THRESHOLD; elsif( or_reduce(RE_Threshold_Ctr) = '0' )then RE_Threshold_Ctr <= (others => '0'); end if; FE_Threshold_Ctr <= FE_Threshold_Ctr - 1; if( Ref_In_FE = '1' )then FE_Threshold_Ctr <= THRESHOLD; elsif( or_reduce(FE_Threshold_Ctr) = '0' )then FE_Threshold_Ctr <= (others => '0'); end if; Ref_Detect <= or_reduce(RE_Threshold_Ctr) and or_reduce(FE_Threshold_Ctr); Ref_Detect_q1 <= Ref_Detect; Ref_Detect_CoS <= Ref_Detect xor Ref_Detect_q1; Interrupt <= Ref_Detect_CoS; end if; end process; end architecture;