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-- Copyright (C) 2002 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
library ieee; use ieee.std_logic_1164.all;
entity nor_gate is
generic ( width : positive;
Tpd01, Tpd10 : delay_length );
port ( input : in std_logic_vector(0 to width - 1);
output : out std_logic );
end entity nor_gate;
architecture primitive of nor_gate is
function max ( a, b : delay_length ) return delay_length is
begin
if a > b then
return a;
else
return b;
end if;
end function max;
begin
reducer : process (input) is
variable result : std_logic;
begin
result := '0';
for index in input'range loop
result := result or input(index);
end loop;
if not result = '1' then
output <= not result after Tpd01;
elsif not result = '0' then
output <= not result after Tpd10;
else
output <= not result after max(Tpd01, Tpd10);
end if;
end process reducer;
end architecture primitive;
library ieee; use ieee.std_logic_1164.all;
library cell_lib;
entity interlock_control is
end entity interlock_control;
-- code from book
architecture detailed_timing of interlock_control is
component nor_gate is
generic ( input_width : positive );
port ( input : in std_logic_vector(0 to input_width - 1);
output : out std_logic );
end component nor_gate;
for ex_interlock_gate : nor_gate
use entity cell_lib.nor_gate(primitive)
generic map ( width => input_width,
Tpd01 => 250 ps, Tpd10 => 200 ps ); -- estimates
-- . . .
-- not in book
signal reg_access_hazard, load_hazard, stall_ex_n : std_logic;
-- end not in book
begin
ex_interlock_gate : component nor_gate
generic map ( input_width => 2 )
port map ( input(0) => reg_access_hazard,
input(1) => load_hazard,
output => stall_ex_n);
-- . . .
-- not in book
reg_access_hazard <= '0' after 10 ns, '1' after 20 ns, 'X' after 30 ns;
load_hazard <= '0' after 2 ns, '1' after 4 ns, 'X' after 6 ns,
'0' after 12 ns, '1' after 14 ns, 'X' after 16 ns,
'0' after 22 ns, '1' after 24 ns, 'X' after 26 ns,
'0' after 32 ns, '1' after 34 ns, 'X' after 36 ns;
-- end not in book
end architecture detailed_timing;
-- end code from book
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