URL
https://opencores.org/ocsvn/btcfpgaminer/btcfpgaminer/trunk
Subversion Repositories btcfpgaminer
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/btcfpgaminer/trunk/c4b.vhd
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-- ------------------------------------------------------------------------ |
-- Copyright (C) 2010 Arif Endro Nugroho |
-- All rights reserved. |
-- |
-- Redistribution and use in source and binary forms, with or without |
-- modification, are permitted provided that the following conditions |
-- are met: |
-- |
-- 1. Redistributions of source code must retain the above copyright |
-- notice, this list of conditions and the following disclaimer. |
-- 2. 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. |
-- |
-- THIS SOFTWARE IS PROVIDED BY ARIF ENDRO NUGROHO "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 ARIF ENDRO NUGROHO 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. |
-- |
-- End Of License. |
-- ------------------------------------------------------------------------ |
library IEEE; |
use IEEE.STD_LOGIC_1164.ALL; |
use ieee.numeric_std.all; |
|
|
entity c4b is |
port ( |
cnt : out bit_vector ( 3 downto 0); |
clk : in std_logic; |
rst : in std_logic |
); |
end c4b; |
|
architecture phy of c4b is |
signal sum : bit_vector ( 3 downto 0); -- sum |
signal cr : bit_vector ( 3 downto 0); -- carry |
begin |
cr(0) <= '0'; -- LSB always zero |
cr(3 downto 1) <= ( ((sum(2 downto 0) and B"001") or (sum(2 downto 0) and cr(2 downto 0))) or (B"001" and cr(2 downto 0)) ); |
process (clk) |
begin |
if (clk = '1' and clk'event) then |
if (rst = '1') then |
sum <= B"0000"; |
else |
sum <= ((sum xor B"0001") xor cr); -- sum = ((addend xor augend) xor carry) |
end if; |
end if; |
end process; |
cnt <= sum; |
end phy; |
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