i want to write vhdl code defining a 2 dimensional matrix (16 * 16 matrix)
but every element in this matrix is an array of 8 ...
and how to write this code in entity...?
You will have to clarify why/where you want to use this.
You can define it as a function and include in a package. This is very similar to C.First define the array and variables and then form the matrix.
For using it in as an entity you will have to clarify what this entity is going to do.