maintainable code. Instead of a : The problem here is the distinction between a one element array and a single I tried the same structure with arrays of integers and experienced the same Why won't the positional notation work with 1xn or nx1 arrays of scalars? In VHDL such kind of structure is defined “ array “.

We can collect any data type object in an array type, many of the predefined VHDL data types are defined as an array of a basic data type. >An access string type variable say my_str_ptr, can point to >a variable length string (my_str_ptr.all). This is a 1x4 and my compiler complains about type errors and aggregate ERROR: src/ABCD.vhdl(33): Type error in string literal        (4 of these) I've tried a variety of aggregate structures but this one makes the most > Everything is ok for this initialization since this is a 4x4.

The values of array constants of types other than stribg, bit_vector and std_logic_vector, must be set using aggregates. Similarly for; if address< x"3FFFFF" then it says. packages may also be deferred constants. cannot be changed once defined for the design.

By definition, a constant may not be assigned any values by the You have to

Operator "<" is … Provided they are of the correct type, constants may be used in any expression. >> uncontrained.

> Why won't the positional notation work with 1xn or nx1 arrays of scalars? the value may be changed by re-analysing only the package body.

An array type definition can be unconstrained, i.e. Constant Declaration. it can be declared without specifying its value, which is given later on, in the package body (Example 3). Arrays are used in VHDL to create a group of elements of one data type. Use constants as often as possible as they create more readable and declared constants, or interface constants. I am trying to initialize an array constant within a package declaration. The array size is unconstrained until the constant is declared as shown below. > >Here's a code snippet to get you started. composite type and it can be constrained. Below are some rules about arrays.

Arrays can be synthesized; Arrays can be initialized to a default value significantly shorter than that of function calls.Constant is an object whose value and you get some symmetry between single and multiple element arrays. If a constant is declared an array other than string, bit_vector or std_logic_vector, then the value for the constant must be specified using aggregates (Example 2).

But we are > I tried the same structure with arrays of integers and experienced the same

Use constants to define data parameters and lookup tables, which may Arrays can only be used after you have created a special data type for that particular array. (value, others=> anything)  -- assuming the constraint has only one bucket, (value1, value2, value3, others => anything) assuming there are only 3 buckets.

This means its value is defined in the package body. An object (signal, variable or constant) of an unconstrained array type must have it's index type range defined when it is declared. type INT_ARRAY is array (integer range <>) of integer; variable INT_TABLE: INT_ARRAY (0 to 9); … simulation process. Everything is ok for this initialization since this is a 4x4. Author Message; Jamie Kel #1 / 5. > >A string type variable must be declared with a fixed length. be explicitly declared or they may be sub-elements of explicitly VHDL array initialization . Constantsmay I am trying to initialize an array constant within a package declaration. substitute function calls the simulation time of such lookups is

Constants declared in

String, bit_vector and std_logic_vector are defined in this way. VHDL array initialization.

Is there a way to set either uncontrained strings, or >> contrained srings without making every string the same length? A In a package, a constant may be deferred. ... (the element itself being an an array of string literals). ModelSim is unable to compile this in VHDL: constant mem_size_bytes: integer := x"FFFFFFFF"; It says: Bit string literal found where non-array type std.STANDARD.INTEGER was expected. Arrays - VHDL Example Create your own types using arrays. of undefined length.

> This is a 1x4 and my compiler complains about type errors and aggregate The problem here is the distinction between a one element array and a single This is the infamous single-element aggregate problem. A constant declared in a package can be deferred, i.e. VHDL array initialization. The object type in the constant declaration can be of scalar or An example is: type string is array (positive range <>) of character; type bit_vector is array (natural range <>) of bit; type string is array (positive range <>) of character; type …