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[/] [open8_urisc/] [trunk/] [VHDL/] [o8_epoch_timer.vhd] - Rev 198
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-- Copyright (c)2011, 2019, 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_epoch_timer -- Description: Provides a 24-bit, 4uS resolution elapsed timer with -- : alarm and interrupt for the Open8 CPU. -- -- Notes : Requires an externally provided uSec tick input - one clock -- : per microsecond. -- -- Register Map: -- Offset Bitfield Description Read/Write -- 0x0 AAAAAAAA B0 of Setpoint (W) or Buffered Time(R) -- 0x1 AAAAAAAA B1 of Setpoint (W) or Buffered Time(R) -- 0x2 AAAAAAAA B2 of Setpoint (W) or Buffered Time(R) -- 0x3 C-----BA Control/Status register (RW) -- A = Update Buffered Time from internal timer (W) -- B = Reset Internal Epoch Time (W) -- C = Alarm State Flag (RW) (write a 1 to clear) -- -- Revision History -- Author Date Change ------------------ -------- --------------------------------------------------- -- Seth Henry 07/28/11 Design Start -- Seth Henry 12/19/19 Renamed to "o8_epoch_timer" to fit "theme" 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_epoch_timer is generic( Reset_Level : std_logic; Address : ADDRESS_TYPE ); port( Clock : in std_logic; Reset : in std_logic; uSec_Tick : in std_logic; -- Bus_Address : in ADDRESS_TYPE; Wr_Enable : in std_logic; Wr_Data : in DATA_TYPE; Rd_Enable : in std_logic; Rd_Data : out DATA_TYPE; Interrupt : out std_logic ); end entity; architecture behave of o8_epoch_timer is constant User_Addr : std_logic_vector(15 downto 2) := Address(15 downto 2); alias Comp_Addr is Bus_Address(15 downto 2); signal Addr_Match : std_logic; alias Reg_Addr is Bus_Address(1 downto 0); signal Reg_Addr_q : std_logic_vector(1 downto 0); signal Wr_En : std_logic; signal Wr_Data_q : DATA_TYPE; signal Rd_En : std_logic; signal epoch_tmr : std_logic_vector(25 downto 0); alias epoch_tmrcmp is epoch_tmr(25 downto 2); signal epoch_buffer : std_logic_vector(23 downto 0); signal epoch_setpt : std_logic_vector(25 downto 0); signal epoch_alarm : std_logic; signal epoch_alarm_q : std_logic; begin Addr_Match <= '1' when Comp_Addr = User_Addr else '0'; io_reg: process( Clock, Reset ) begin if( Reset = Reset_Level )then epoch_tmr <= (others => '0'); epoch_buffer <= (others => '0'); epoch_setpt <= (others => '0'); epoch_alarm <= '0'; epoch_alarm_q <= '0'; Wr_Data_q <= (others => '0'); Reg_Addr_q <= (others => '0'); Wr_En <= '0'; Rd_En <= '0'; Rd_Data <= OPEN8_NULLBUS; Interrupt <= '0'; elsif( rising_edge( Clock ) )then epoch_tmr <= epoch_tmr + uSec_Tick; -- Force the lower bits of the setpoint to "11" so that the offset is -- reduced to 1uS (reproducing the original behavior). Software should -- always subtract 4uS (-1) from the desired time to compensate epoch_setpt(1 downto 0) <= "11"; Reg_Addr_q <= Reg_Addr; Wr_Data_q <= Wr_Data; Wr_En <= Addr_Match and Wr_Enable; if( Wr_En = '1' and or_reduce(Reg_Addr_q) = '0' )then epoch_buffer <= epoch_tmrcmp(25 downto 2); end if; if( Wr_En = '1' )then case( Reg_Addr_q )is when "00" => epoch_setpt(9 downto 2) <= Wr_Data_q; when "01" => epoch_setpt(17 downto 10) <= Wr_Data_q; when "10" => epoch_setpt(25 downto 18) <= Wr_Data_q; when "11" => if( Wr_Data_q(0) = '1' )then epoch_buffer <= epoch_tmrcmp; end if; if( Wr_Data_q(1) = '1' )then epoch_tmr <= (others => '0'); end if; if( Wr_Data_q(7) = '1' )then epoch_alarm <= '0'; end if; when others => null; end case; end if; -- Set and hold on alarm condition if( epoch_tmr > epoch_setpt )then epoch_alarm <= '1'; end if; epoch_alarm_q <= epoch_alarm; -- Fire on rising edge of epoch_alarm Interrupt <= epoch_alarm and not epoch_alarm_q; Rd_Data <= OPEN8_NULLBUS; Rd_En <= Addr_Match and Rd_Enable; if( Rd_En = '1' )then case( Reg_Addr_q )is when "00" => Rd_Data <= epoch_buffer(7 downto 0); when "01" => Rd_Data <= epoch_buffer(15 downto 8); when "10" => Rd_Data <= epoch_buffer(23 downto 16); when "11" => Rd_Data <= epoch_alarm & "0000000"; when others => null; end case; end if; end if; end process; end architecture;
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