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vhdl-sincos-gen
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* Reduce width of sin/cos input to multiplier by 1 bit. 

* This has no significant effect on accuracy, but reduces multiplier width.
This commit is contained in:
Joris van Rantwijk 2016-04-14 00:05:52 +02:00
parent 9f4bb7f9b0
commit 2dbc6d44db
1 changed files with 18 additions and 18 deletions
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36
rtl/sincos_gen.vhdl
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@ -60,12 +60,12 @@ architecture rtl of sincos_gen is
constant dphase_bits: integer := phase_bits - table_addrbits;
-- Scaling for 1st order (final) Taylor correction.
constant accum1_bits: integer := table_width + phase_bits;
constant round_const1: unsigned(phase_bits-2 downto 0) := (others => '1');
constant accum1_bits: integer := table_width + phase_bits - 1;
constant round_const1: unsigned(phase_bits-3 downto 0) := (others => '1');
-- Scaling for 2nd order Taylor correction.
constant accum2_bits: integer := table_width + phase_bits + 1;
constant round_const2: unsigned(phase_bits-1 downto 0) := "0" & round_const1;
constant accum2_bits: integer := table_width + phase_bits;
constant round_const2: unsigned(phase_bits-2 downto 0) := "0" & round_const1;
-- Lookup table type.
type table_type is array(0 to table_size-1) of
@ -104,17 +104,17 @@ architecture rtl of sincos_gen is
signal r3_dphase: signed(dphase_bits-1 downto 0);
signal r3_sin_data: unsigned(table_width-1 downto 0);
signal r3_cos_data: unsigned(table_width-1 downto 0);
signal r3_sinm2_a: signed(table_width downto 0);
signal r3_sinm2_a: signed(table_width-1 downto 0);
signal r3_sinm2_b: signed(dphase_bits-1 downto 0);
signal r3_cosm2_a: signed(table_width downto 0);
signal r3_cosm2_a: signed(table_width-1 downto 0);
signal r3_cosm2_b: signed(dphase_bits-1 downto 0);
signal r4_quadrant: unsigned(1 downto 0);
signal r4_dphase: signed(dphase_bits-1 downto 0);
signal r4_sin_data: unsigned(table_width-1 downto 0);
signal r4_cos_data: unsigned(table_width-1 downto 0);
signal r4_sinm2_m: signed(table_width+dphase_bits downto 0);
signal r4_sinm2_m: signed(table_width+dphase_bits-1 downto 0);
signal r4_sinm2_c: signed(accum2_bits-1 downto 0);
signal r4_cosm2_m: signed(table_width+dphase_bits downto 0);
signal r4_cosm2_m: signed(table_width+dphase_bits-1 downto 0);
signal r4_cosm2_c: signed(accum2_bits-1 downto 0);
signal r5_quadrant: unsigned(1 downto 0);
signal r5_dphase: signed(dphase_bits-1 downto 0);
@ -125,14 +125,14 @@ architecture rtl of sincos_gen is
signal r6_quadrant: unsigned(1 downto 0);
signal r6_sin_data: unsigned(table_width-1 downto 0);
signal r6_cos_data: unsigned(table_width-1 downto 0);
signal r6_sinm1_a: signed(table_width downto 0);
signal r6_sinm1_a: signed(table_width-1 downto 0);
signal r6_sinm1_b: signed(dphase_bits-1 downto 0);
signal r6_cosm1_a: signed(table_width downto 0);
signal r6_cosm1_a: signed(table_width-1 downto 0);
signal r6_cosm1_b: signed(dphase_bits-1 downto 0);
signal r7_quadrant: unsigned(1 downto 0);
signal r7_sinm1_m: signed(table_width+dphase_bits downto 0);
signal r7_sinm1_m: signed(table_width+dphase_bits-1 downto 0);
signal r7_sinm1_c: signed(accum1_bits-1 downto 0);
signal r7_cosm1_m: signed(table_width+dphase_bits downto 0);
signal r7_cosm1_m: signed(table_width+dphase_bits-1 downto 0);
signal r7_cosm1_c: signed(accum1_bits-1 downto 0);
signal r8_quadrant: unsigned(1 downto 0);
signal r8_sinm1_p: signed(accum1_bits-1 downto 0);
@ -275,9 +275,9 @@ begin
r3_cos_data <= r2_cos_data;
-- Prepare multiplication for 2nd order Taylor correction.
r3_sinm2_a <= signed(resize(r2_sin_data, table_width+1));
r3_sinm2_a <= signed(resize(r2_sin_data(table_width-1 downto 1), table_width));
r3_sinm2_b <= v3_dphase;
r3_cosm2_a <= signed(resize(r2_cos_data, table_width+1));
r3_cosm2_a <= signed(resize(r2_cos_data(table_width-1 downto 1), table_width));
r3_cosm2_b <= v3_dphase;
-- Stage 4
@ -341,9 +341,9 @@ begin
r6_cos_data <= r2_cos_data;
-- Prepare multiplication for 1st order Taylor correction.
r6_sinm1_a <= signed(resize(r2_cos_data, table_width+1));
r6_sinm1_a <= signed(resize(r2_cos_data(table_width-1 downto 1), table_width));
r6_sinm1_b <= v3_dphase;
r6_cosm1_a <= signed(resize(r2_sin_data, table_width+1));
r6_cosm1_a <= signed(resize(r2_sin_data(table_width-1 downto 1), table_width));
r6_cosm1_b <= v3_dphase;
end if;
@ -378,8 +378,8 @@ begin
-- Stage 9
-- Extract relevant bits of answer.
v9_sin_val := r8_sinm1_p(accum1_bits-1 downto phase_bits);
v9_cos_val := r8_cosm1_p(accum1_bits-1 downto phase_bits);
v9_sin_val := r8_sinm1_p(accum1_bits-1 downto phase_bits-1);
v9_cos_val := r8_cosm1_p(accum1_bits-1 downto phase_bits-1);
-- Choose between sin/cos based on quadrant.
if r8_quadrant(0) = '0' then