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+
+-- Copyright (C) 1996 Morgan Kaufmann Publishers, Inc
+
+-- This file is part of VESTs (Vhdl tESTs).
+
+-- VESTs is free software; you can redistribute it and/or modify it
+-- under the terms of the GNU General Public License as published by the
+-- Free Software Foundation; either version 2 of the License, or (at
+-- your option) any later version.
+
+-- VESTs 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 more details.
+
+-- You should have received a copy of the GNU General Public License
+-- along with VESTs; if not, write to the Free Software Foundation,
+-- Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+
+-- ---------------------------------------------------------------------
+--
+-- $Id: ap_a_ap_a_08.vhd,v 1.2 2001-10-26 16:29:33 paw Exp $
+-- $Revision: 1.2 $
+--
+-- ---------------------------------------------------------------------
+
+library ieee; use ieee.std_logic_1164.all;
+
+ entity entname is
+ end entity entname;
+
+
+
+ architecture rtl of entname is
+
+ -- code from book
+
+ subtype state_type is std_ulogic_vector(3 downto 0);
+ constant s0 : state_type := "0001";
+ constant s1 : state_type := "0010";
+ constant s2 : state_type := "0100";
+ constant s3 : state_type := "1000";
+
+ -- end code from book
+
+ signal state, next_state : state_type;
+ signal con1, con2, con3 : std_ulogic;
+ signal out1, out2 : std_ulogic;
+ signal clk, reset : std_ulogic;
+
+ begin
+ state_logic : process (state, con1, con2, con3) is
+ begin
+ case state is
+ when s0 =>
+ out1 <= '0';
+ out2 <= '0';
+ next_state <= s1;
+ when s1 =>
+ out1 <= '1';
+ if con1 = '1' then
+ next_state <= s2;
+ else
+ next_state <= s1;
+ end if;
+ when s2 =>
+ out2 <= '1';
+ next_state <= s3;
+ when s3 =>
+ if con2 = '0' then
+ next_state <= s3;
+ elsif con3 = '0' then
+ out1 <= '0';
+ next_state <= s2;
+ else
+ next_state <= s1;
+ end if;
+ when others =>
+ null;
+ end case;
+ end process state_logic;
+
+ state_register : process (clk, reset) is
+ begin
+ if reset = '0' then
+ state <= s0;
+ elsif rising_edge(clk) then
+ state <= next_state;
+ end if;
+ end process state_register;
+
+
+ clk_gen : process is
+ begin
+ clk <= '0', '1' after 10 ns;
+ wait for 20 ns;
+ end process clk_gen;
+
+ reset <= '0', '1' after 40 ns;
+
+ con1 <= '0', '1' after 100 ns, '0' after 120 ns;
+
+ con2 <= '0', '1' after 160 ns;
+
+ con3 <= '0', '1' after 220 ns;
+
+
+ end architecture rtl;