Data commit

Task/Arrays/VHDL/arrays.vhdl

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+entity Array_Test is
+end entity Array_Test;
+
+architecture Example of Array_test is
+
+   -- Array type have to be defined first
+   type Integer_Array is array (Integer range <>) of Integer;
+
+   -- Array index range can be ascending...
+   signal A : Integer_Array (1 to 20);
+
+   -- or descending
+   signal B : Integer_Array (20 downto 1);
+
+   -- VHDL array index ranges may begin at any value, not just 0 or 1
+   signal C : Integer_Array (-37 to 20);
+
+   -- VHDL arrays may be indexed by enumerated types, which are
+   -- discrete non-numeric types
+   type Days is (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
+   type Activities is (Work, Fish);
+   type Daily_Activities is array (Days) of Activities;
+   signal This_Week : Daily_Activities := (Mon to Fri => Work, Others => Fish);
+
+   type Finger is range 1 to 4; -- exclude thumb
+   type Fingers_Extended is array (Finger) of Boolean;
+   signal Extended : Fingers_Extended;
+
+   -- Array types may be unconstrained.
+   -- Objects of the type must be constrained
+   type Arr is array (Integer range <>) of Integer;
+   signal Uninitialized : Arr (1 to 10);
+   signal Initialized_1 : Arr (1 to 20) := (others => 1);
+   constant Initialized_2 : Arr := (1 to 30 => 2);
+   constant Const : Arr := (1 to 10 => 1, 11 to 20 => 2, 21 | 22 => 3);
+   signal Centered : Arr (-50 to 50) := (0 => 1, others => 0);
+
+   signal Result : Integer;
+
+begin
+
+   A <= (others => 0);           -- Assign whole array
+   B <= (1 => 1, 2 => 1,
+         3 => 2, others => 0);   -- Assign whole array, different values
+   A (1) <= -1;                  -- Assign individual element
+   A (2 to 4) <= B (3 downto 1); -- Assign a slice
+   A (3 to 5) <= (2, 4, -1);     -- Assign an aggregate
+   A (3 to 5) <= A (4 to 6);     -- It is OK to overlap slices when assigned
+
+   -- VHDL arrays does not have 'first' and 'last' elements,
+   -- but have 'Left' and 'Right' instead
+   Extended (Extended'Left)  <= False; -- Set leftmost element of array
+   Extended (Extended'Right) <= False; -- Set rightmost element of array
+
+   Result <= A (A'Low) + B (B'High);
+
+end architecture Example;