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[/] [cordic/] [trunk/] [rect2polar/] [r2p_post.vhd] - Blame information for rev 13

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--
--      post.vhd
--
--      Cordic post-processing block
--
-- Compensate cordic algorithm K-factor; divide Radius by 1.6467, or multiply by 0.60725. 
-- Approximation:  Ra = Ri/2 + Ri/8 - Ri/64 - Ri/512
--                 Radius = Ra - Ra/4096 = Ri * 0.60727. This is a 0.0034% error.
-- Implementation: Ra = (Ri/2 + Ri/8) - (Ri/64 + Ri/512)
--                 Radius = Ra - Ra/4096
--      Position calculated angle in correct quadrant.
--
 
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
 
entity r2p_post is
        port(
                clk     : in std_logic;
                ena     : in std_logic;
 
                Ai      : in signed(19 downto 0);
                Ri      : in unsigned(19 downto 0);
                Q       : in std_logic_vector(2 downto 0);
 
                Ao      : out signed(19 downto 0);
                Ro      : out unsigned(19 downto 0));
end entity r2p_post;
 
architecture dataflow of r2p_post is
begin
        radius: block
                signal RadA, RadB, RadC : unsigned(19 downto 0);
        begin
                process(clk)
                begin
                        if (clk'event and clk = '1') then
                                if (ena = '1') then
                                        RadA <= ('0' & Ri(19 downto 1)) + ("000" & Ri(19 downto 3));
                                        RadB <= ("000000" & Ri(19 downto 6)) + ("000000000" & Ri(19 downto 9));
                                        RadC <= RadA - RadB;
 
                                        Ro <= RadC - RadC(19 downto 12);
                                end if;
                        end if;
                end process;
        end block radius;
 
        angle: block
                constant const_PI2 : signed(19 downto 0) := conv_signed(16#40000#, 20); -- PI / 2
                constant const_PI : signed(19 downto 0) := conv_signed(16#80000#, 20);  -- PI
                constant const_2PI : signed(19 downto 0) := (others => '0');            -- 2PI
 
                signal dQ : std_logic_vector(2 downto 1);
                signal ddQ : std_logic;
                signal AngStep1 : signed(19 downto 0);
                signal AngStep2 : signed(19 downto 0);
        begin
                angle_step1: process(clk, Ai, Q)
                        variable overflow : std_logic;
                        variable AngA, AngB, Ang : signed(19 downto 0);
                begin
                        -- check if angle is negative, if so set it to zero
                        overflow := Ai(19); --and Ai(18);
 
                        if (overflow = '1') then
                                AngA := (others => '0');
                        else
                                AngA := Ai;
                        end if;
 
                        -- step 1: Xabs and Yabs are swapped
                        -- Calculated angle is the angle between vector and Y-axis.
                        -- ActualAngle = PI/2 - CalculatedAngle
                        AngB := const_PI2 - AngA;
 
                        if (Q(0) = '1') then
                                Ang := AngB;
                        else
                                Ang := AngA;
                        end if;
 
                        if (clk'event and clk = '1') then
                                if (ena = '1') then
                                        AngStep1 <= Ang;
                                        dQ <= q(2 downto 1);
                                end if;
                        end if;
                end process angle_step1;
 
 
                angle_step2: process(clk, AngStep1, dQ)
                        variable AngA, AngB, Ang : signed(19 downto 0);
                begin
                        AngA := AngStep1;
 
                        -- step 2: Xvalue is negative
                        -- Actual angle is in the second or third quadrant
                        -- ActualAngle = PI - CalculatedAngle
                        AngB := const_PI - AngA;
 
                        if (dQ(1) = '1') then
                                Ang := AngB;
                        else
                                Ang := AngA;
                        end if;
 
                        if (clk'event and clk = '1') then
                                if (ena = '1') then
                                        AngStep2 <= Ang;
                                        ddQ <= dQ(2);
                                end if;
                        end if;
                end process angle_step2;
 
 
                angle_step3: process(clk, AngStep2, ddQ)
                        variable AngA, AngB, Ang : signed(19 downto 0);
                begin
                        AngA := AngStep2;
 
                        -- step 3: Yvalue is negative
                        -- Actual angle is in the third or fourth quadrant
                        -- ActualAngle = 2PI - CalculatedAngle
                        AngB := const_2PI - AngA;
 
                        if (ddQ = '1') then
                                Ang := AngB;
                        else
                                Ang := AngA;
                        end if;
 
                        if (clk'event and clk = '1') then
                                if (ena = '1') then
                                        Ao <= Ang;
                                end if;
                        end if;
                end process angle_step3;
        end block angle;
end;
 
 
 
 
 
 
 
 
 

Line No.	Rev	Author	Line
1	6	rherveille	`--`
2			`-- post.vhd`
3			`--`
4			`-- Cordic post-processing block`
5			`--`
6			`-- Compensate cordic algorithm K-factor; divide Radius by 1.6467, or multiply by 0.60725.`
7			`-- Approximation: Ra = Ri/2 + Ri/8 - Ri/64 - Ri/512`
8			`-- Radius = Ra - Ra/4096 = Ri * 0.60727. This is a 0.0034% error.`
9			`-- Implementation: Ra = (Ri/2 + Ri/8) - (Ri/64 + Ri/512)`
10			`-- Radius = Ra - Ra/4096`
11			`-- Position calculated angle in correct quadrant.`
12			`--`
13
14			`library ieee;`
15			`use ieee.std_logic_1164.all;`
16			`use ieee.std_logic_arith.all;`
17
18			`entity r2p_post is`
19			`port(`
20			`clk : in std_logic;`
21			`ena : in std_logic;`
22
23			`Ai : in signed(19 downto 0);`
24			`Ri : in unsigned(19 downto 0);`
25			`Q : in std_logic_vector(2 downto 0);`
26
27			`Ao : out signed(19 downto 0);`
28			`Ro : out unsigned(19 downto 0));`
29			`end entity r2p_post;`
30
31			`architecture dataflow of r2p_post is`
32			`begin`
33			`radius: block`
34			`signal RadA, RadB, RadC : unsigned(19 downto 0);`
35			`begin`
36			`process(clk)`
37			`begin`
38			`if (clk'event and clk = '1') then`
39			`if (ena = '1') then`
40			`RadA <= ('0' & Ri(19 downto 1)) + ("000" & Ri(19 downto 3));`
41			`RadB <= ("000000" & Ri(19 downto 6)) + ("000000000" & Ri(19 downto 9));`
42			`RadC <= RadA - RadB;`
43
44			`Ro <= RadC - RadC(19 downto 12);`
45			`end if;`
46			`end if;`
47			`end process;`
48			`end block radius;`
49
50			`angle: block`
51			`constant const_PI2 : signed(19 downto 0) := conv_signed(16#40000#, 20); -- PI / 2`
52			`constant const_PI : signed(19 downto 0) := conv_signed(16#80000#, 20); -- PI`
53			`constant const_2PI : signed(19 downto 0) := (others => '0'); -- 2PI`
54
55			`signal dQ : std_logic_vector(2 downto 1);`
56			`signal ddQ : std_logic;`
57			`signal AngStep1 : signed(19 downto 0);`
58			`signal AngStep2 : signed(19 downto 0);`
59			`begin`
60			`angle_step1: process(clk, Ai, Q)`
61			`variable overflow : std_logic;`
62			`variable AngA, AngB, Ang : signed(19 downto 0);`
63			`begin`
64			`-- check if angle is negative, if so set it to zero`
65			`overflow := Ai(19); --and Ai(18);`
66
67			`if (overflow = '1') then`
68			`AngA := (others => '0');`
69			`else`
70			`AngA := Ai;`
71			`end if;`
72
73			`-- step 1: Xabs and Yabs are swapped`
74			`-- Calculated angle is the angle between vector and Y-axis.`
75			`-- ActualAngle = PI/2 - CalculatedAngle`
76			`AngB := const_PI2 - AngA;`
77
78			`if (Q(0) = '1') then`
79			`Ang := AngB;`
80			`else`
81			`Ang := AngA;`
82			`end if;`
83
84			`if (clk'event and clk = '1') then`
85			`if (ena = '1') then`
86			`AngStep1 <= Ang;`
87			`dQ <= q(2 downto 1);`
88			`end if;`
89			`end if;`
90			`end process angle_step1;`
91
92
93			`angle_step2: process(clk, AngStep1, dQ)`
94			`variable AngA, AngB, Ang : signed(19 downto 0);`
95			`begin`
96			`AngA := AngStep1;`
97
98			`-- step 2: Xvalue is negative`
99			`-- Actual angle is in the second or third quadrant`
100			`-- ActualAngle = PI - CalculatedAngle`
101			`AngB := const_PI - AngA;`
102
103			`if (dQ(1) = '1') then`
104			`Ang := AngB;`
105			`else`
106			`Ang := AngA;`
107			`end if;`
108
109			`if (clk'event and clk = '1') then`
110			`if (ena = '1') then`
111			`AngStep2 <= Ang;`
112			`ddQ <= dQ(2);`
113			`end if;`
114			`end if;`
115			`end process angle_step2;`
116
117
118			`angle_step3: process(clk, AngStep2, ddQ)`
119			`variable AngA, AngB, Ang : signed(19 downto 0);`
120			`begin`
121			`AngA := AngStep2;`
122
123			`-- step 3: Yvalue is negative`
124			`-- Actual angle is in the third or fourth quadrant`
125			`-- ActualAngle = 2PI - CalculatedAngle`
126			`AngB := const_2PI - AngA;`
127
128			`if (ddQ = '1') then`
129			`Ang := AngB;`
130			`else`
131			`Ang := AngA;`
132			`end if;`
133
134			`if (clk'event and clk = '1') then`
135			`if (ena = '1') then`
136			`Ao <= Ang;`
137			`end if;`
138			`end if;`
139			`end process angle_step3;`
140			`end block angle;`
141			`end;`
142
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[/] [cordic/] [trunk/] [rect2polar/] [r2p_post.vhd] - Blame information for rev 13