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[/] [xmatchpro/] [trunk/] [xmw4-comdec/] [src/] [bsl_tc_2_d.vhd] - Rev 8
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--This library is free software; you can redistribute it and/or --modify it under the terms of the GNU Lesser General Public --License as published by the Free Software Foundation; either --version 2.1 of the License, or (at your option) any later version. --This library 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 --Lesser General Public License for more details. --You should have received a copy of the GNU Lesser General Public --License along with this library; if not, write to the Free Software --Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA -- e_mail : j.l.nunez-yanez@byacom.co.uk --------------------------------- -- ENTITY = BSL_TC_2 -- -- version = 2.0 -- -- last update = 22/05/00 -- -- author = Jose Nunez -- --------------------------------- -- FUNCTION -- Latches the block size synchronously under the control of -- the LOAD signal (active LOW). The 16 bit number indicates the number of -- tuples in the block. -- The tuple counter is fully synchronous and is incremented on each -- clock cycle if INC signal is LOW. -- When the tuple counter reaches the required number of tuples within -- the block minus one, the END OF BLOCK signal is activated. The counter -- then remains locked in this state until cleared or reset. -- PIN LIST -- BLOCK_SIZE = input block size -- LOAD = load block size (active LOW) -- INC = increment tuple counter (active LOW) -- CLEAR = asynchronously clear the tuple counter (active LOW) and the block size -- CLK = clock -- EO_BLOCK = end of block signal (active LOW) -- WARNING - dzx.bit_arith is an INTERGRAPH SPECIFIC LIBRARY -- take note of this if porting to another system! -- It is required to allow the addition of two bit -- vectors in the process TUPLE_COUNTER. library ieee,dzx; use ieee.std_logic_1164.all; use dzx.bit_arith.all; use dzx.attributes.all; entity BSL_TC_2_D is port ( BLOCK_SIZE : in bit_vector(31 downto 0) ; INC : in bit ; CLEAR : in bit ; RESET : in bit; CLK : in bit ; EO_BLOCK : out bit ; FINISH_D_BUFFERS : out bit ); end BSL_TC_2_D; architecture COUNTER of BSL_TC_2_D is -- indicates end of block (active LOW), i.e tuple count is equal -- to decoded block size signal EOB : bit; -- indicates the number of tuples that have been processed signal TUPLE_COUNT : bit_vector(29 downto 0); begin TUPLE_COUNTER : process(CLK,CLEAR) begin -- Since the increment is always with 4 bytes I use only 14 bit counter if (CLEAR = '0') then TUPLE_COUNT <= "000000000000000000000000000000"; elsif ((CLK'event) and (CLK='1')) then if (RESET = '0') then TUPLE_COUNT <= "000000000000000000000000000000"; elsif ((INC = '1') and (EOB = '1')) then TUPLE_COUNT <= TUPLE_COUNT + "000000000000000000000000000001"; end if; end if; end process TUPLE_COUNTER; END_OF_BLOCK : process (TUPLE_COUNT, BLOCK_SIZE) begin if ((TUPLE_COUNT & "00") >= BLOCK_SIZE) then EOB <= '0'; else EOB <= '1'; end if; end process END_OF_BLOCK; -- assign EOB to external EO_BLOCK signal EO_BLOCK <= EOB; -- or not(INC); -- to stop the buffers when the last data has been read from them -- FINISH_D_BUFFERS <= '0' when (TUPLE_COUNT & "00" + "0000000000001100" = BS_LATCH) else '1'; FINISH_D_BUFFERS <= EOB; end COUNTER;