ARRAYS

Hi Friends,

This post will be covering array concept in systemverilog. 

Systemverilog supports packed and un-packed arrays of data. 

"Packed array" refer to the dimensions declared before identifier.

Example:

reg [0:3] array_variable;// 1-dimensional packed array

wire [31:0] [1:0] vari; // 2-dimensional packed array

"Un-packed array" refer to the dimension declared after identifier. 

Example:

reg array_variable[0:3];// 1-dimensional unpacked array of integers

integer matrix[7:0][0:31][15:0]; // 3-dimensional unpacked array of integers

integer matrix[8][32][16]; // 3-dimensional unpacked array of integers 

  

An array hold a fixed number of equally-sized data elements. Individual elements are accessed by index using a consecutive range of integers.  Some type of arrays allows to access individual elements using non consecutive values of any data types.  Arrays can be classified as fixed-sized arrays (sometimes known as static arrays) whose size cannot change once their declaration is done, or dynamic arrays, which can be resized. 

Fixed Arrays: 

Fixed size array are created at compilation time. SystemVerilog accepts a single number, as an alternative to a range, to specify the size of an unpacked array. That is, [size] becomes the same as [0:size-1]. 

Example:

   int Array[8][32]; is the same as: int Array[0:7][0:31];

Memories:

A one-dimensional array with elements of types reg, logic, or bit is also called a memory

  
Example:
    

logic [7:0] mema [0:255]; // declares a memory array of 256 8-bit

                                          // elements. The array indices are 0 to 255

mema[5] = 0; // Write to word at address 5

data = mema[addr]; // Read word at address indexed by addr

Operations On Arrays 

The following operations can be performed on all arrays, packed or unpacked:
1. Reading and writing the array, e.g., A = B

2. Reading and writing a slice of the array, e.g., A[i:j] = B[i:j]

3. Reading and writing a variable slice of the array, e.g., A[x+:c] = B[y+:c]

4. Reading and writing an element of the array, e.g., A[i] = B[i]

5. Equality operations on the array or slice of the array, e.g., A==B, A[i:j] != B[i:j]

Thank You,

Moderator.