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[/] [astron_requantizer/] [trunk/] [common_round.vhd] - Rev 2
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------------------------------------------------------------------------------- -- -- Copyright (C) 2009 -- ASTRON (Netherlands Institute for Radio Astronomy) <http://www.astron.nl/> -- P.O.Box 2, 7990 AA Dwingeloo, The Netherlands -- -- This program 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 3 of the License, or -- (at your option) any later version. -- -- This program 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 this program. If not, see <http://www.gnu.org/licenses/>. -- ------------------------------------------------------------------------------- LIBRARY ieee, common_pkg_lib, common_components_lib; USE ieee.std_logic_1164.ALL; USE ieee.numeric_std.ALL; USE common_pkg_lib.common_pkg.ALL; ENTITY common_round IS -- -- ISE XST results for rounding 36b --> 18b: -- int clip --> slices FFs LUTs -- 1) signed TRUE 63 54 80 -- increases with input widths > 18b -- 2) signed FALSE 59 54 73 -- increases with input widths > 18b -- 3) unsigned TRUE 34 37 43 -- same for all input widths > 18b -- 4) unsigned FALSE 21 37 19 -- same for all input widths > 18b -- -- If the input comes from a product and is rounded to the input width then g_round_clip can safely be FALSE, because e.g. for unsigned -- 4b*4b=8b->4b the maximum product is 15*15=225 <= 255-8, so wrapping will never occur. -- GENERIC ( g_representation : STRING := "SIGNED"; -- SIGNED (round +-0.5 away from zero to +- infinity) or UNSIGNED rounding (round 0.5 up to + inifinity) g_round : BOOLEAN := TRUE; -- when TRUE round the input, else truncate the input g_round_clip : BOOLEAN := FALSE; -- when TRUE clip rounded input >= +max to avoid wrapping to output -min (signed) or 0 (unsigned) g_pipeline_input : NATURAL := 0; -- >= 0 g_pipeline_output : NATURAL := 1; -- >= 0, use g_pipeline_input=0 and g_pipeline_output=0 for combinatorial output g_in_dat_w : NATURAL := 36; g_out_dat_w : NATURAL := 18 ); PORT ( clk : IN STD_LOGIC; clken : IN STD_LOGIC := '1'; in_dat : IN STD_LOGIC_VECTOR(g_in_dat_w-1 DOWNTO 0); out_dat : OUT STD_LOGIC_VECTOR(g_out_dat_w-1 DOWNTO 0) ); END; ARCHITECTURE rtl OF common_round IS CONSTANT c_remove_w : INTEGER := g_in_dat_w-g_out_dat_w; SIGNAL reg_dat : STD_LOGIC_VECTOR(in_dat'RANGE); SIGNAL res_dat : STD_LOGIC_VECTOR(out_dat'RANGE); BEGIN u_input_pipe : ENTITY common_components_lib.common_pipeline GENERIC MAP ( g_representation => g_representation, g_pipeline => g_pipeline_input, g_in_dat_w => g_in_dat_w, g_out_dat_w => g_in_dat_w ) PORT MAP ( clk => clk, clken => clken, in_dat => in_dat, out_dat => reg_dat ); -- Increase to out_dat width no_s : IF c_remove_w<=0 AND g_representation="SIGNED" GENERATE res_dat <= RESIZE_SVEC(reg_dat, g_out_dat_w); END GENERATE; no_u : IF c_remove_w<=0 AND g_representation="UNSIGNED" GENERATE res_dat <= RESIZE_UVEC(reg_dat, g_out_dat_w); END GENERATE; -- Decrease to out_dat width by c_remove_w number of LSbits -- . rounding gen_s : IF c_remove_w>0 AND g_round=TRUE AND g_representation="SIGNED" GENERATE res_dat <= s_round(reg_dat, c_remove_w, g_round_clip); END GENERATE; gen_u : IF c_remove_w>0 AND g_round=TRUE AND g_representation="UNSIGNED" GENERATE res_dat <= u_round(reg_dat, c_remove_w, g_round_clip); END GENERATE; -- . truncating gen_t : IF c_remove_w>0 AND g_round=FALSE GENERATE res_dat <= truncate(reg_dat, c_remove_w); END GENERATE; u_output_pipe : ENTITY common_components_lib.common_pipeline GENERIC MAP ( g_representation => g_representation, g_pipeline => g_pipeline_output, g_in_dat_w => g_out_dat_w, g_out_dat_w => g_out_dat_w ) PORT MAP ( clk => clk, clken => clken, in_dat => res_dat, out_dat => out_dat ); END rtl;
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