Data types

Question 1

New data type advntges

Answer 1

Added new datatypes :

• 2-state data types
• Strings
• with built-in searching/sorting support ( Q,dyn_arr,asso_arr)
• which are Abstract data structures ( classes,structs)
• with Multiple view of same data ( union/packed array)
• which are Easy to WR/RD : enum

Question 2

Logic

Answer 2

Can be used anywhere, in place of nets/registers.

Except : more than one structural drivers

assign l1 = a&b;
assign l1 = c|d;

Question 3

All data types

Answer 3

• bit : 1 : 2-state : unsigned
• logic : 1 : 4-state : unsigned

byte : 8 : 2-state : signed
shortint : 16 : 2-state : signed
int : 32 : 2-state : signed
longint : 64 : 2-state : signed
real : 64 : 2-state : signed
* integer : 32 : 4-state : signed
* time : 64

Question 4

Built-in function

Answer 4

• $isunknown( var ) : returns 1 is XorZ in var
• $timeformat()
• $size() : Returns size of array

Question 5

Fixed Array

Answer 5

Fixed array

• Declaration : type name[size];
  type name[0:size-1];
  eg : int arr[5] ::::= int arr[0:5]

                 int arr[5] = '{ 20,21,22,23,24};    // same as ==  int arr[0:4]
                    Here arr[0] = 20
                         arr[1] = 21
                    foreach(arr[i])  : starts with arr[0],arr[1]...arr[4]
  
                 int arr[4:0] = '{ 20,21,22,23,24};
                    Here arr[0] = 24
                         arr[1] = 23
                    foreach(arr[i])  : starts with arr[4],arr[3]...arr[0]

• Initialization : arr = ‘{ 20,21,3{-1}};
  arr = ‘{ 20,21,default:-1};
• size : $size(arr)
• Accessing : foreach(arr[i]) begin arr[i]=-1; end```
  int arr_2d[3][2] = ‘{‘{00,01}, ‘{10,11}, ‘{20,21}};
  foreach(arr_2d[i,j]) begin … end
  foreach(arr_2d[i]) begin foreach(arr_2d[,j]) begin … end end
  ~~~
• Compare/copy : If arrays of same type & size

Question 6

Array which is packed

Answer 6

Unpacked ::
~~~
logic[7:0] u_arr1[4] -
——–——–——–bbbbbbbbb : u_arr1[0] : word0
——–——–——–bbbbbbbbb : u_arr1[1] : word1
——–——–——–bbbbbbbbb : u_arr1[2] : word2
——–——–_——–_bbbbbbbbb : u_arr1[3] : word3
~~~

Packed :: logic[3:0][7:0] p_arr1 - bbbbbbbb_bbbbbbbb_bbbbbbbb_bbbbbbbbb : p_arr1 : word0

logic[7:0]      u_arr1[4]   = '{ 8'haa, 8'hbb, 8'hcc, 8'hdd};
logic[7:0]      u_arr2[3:0] = '{ 8'haa, 8'hbb, 8'hcc, 8'hdd};
logic[3:0][7:0] p_arr1 = 32'haabbccdd;
logic[4][7:0]   p_arr2 = 32'haabbccdd;

u_arr1[0] :=  8'haa 
u_arr2[0] :=  8'hdd 

p_arr1[0] :=  8'hdd 
p_arr2[0] :=  8'haa 

Use of packed array :
* Multiple view of same data
* @(packed_array) : wait condition

Question 7

when is subscript needed after array

Answer 7

• Depends on number of dimension defined after name
• Page 33-34

Question 8

2d array indexing

Answer 8

• [i,j], [,j] allowed only in foreach.
• not allowed even in body of foreach
• page : 30,31

Question 9

Dynamin array

Answer 9

• declaration syntax
• initialization
• size
• accessing elements
• compare/copy
• Built-in functions
• usage
• Page - 35, notebook(ruled)

Question 10

when is new not needed for dyn array

Answer 10

page 35

Question 11

Mutli-D dyn array

Answer 11

• Regular/irregular dyn array
• https://verificationguide.com/systemverilog/systemverilog-multidimensional-dynamic-array/

bit [7:0] d_array[][];
  
  initial begin
    //memory allocation
    d_array = new[3];
    
    d_array[0] = new[2];
    d_array[1] = new[1];
    d_array[2] = new[4];
    
    //assigning random value to elements
    foreach(d_array[i,j]) d_array[i][j] = $random;
    
    //displaying array elements
    foreach(d_array[i,j])   
      $display("\td_aaray[%0d,%0d] = %0d",i,j, d_array[i][j]);
  end

Question 12

fixed and dynamic array copies

Answer 12

• notebook

Question 13

Queues

Answer 13

• declaration syntax
• initialization
• size
• indexing
• copy/compare
• builtin function
• usage
• notes/page-37

Question 14

$ to access last element

Answer 14

• applicable only to q
• examples
• note/page37

Question 15

associative array

Answer 15

• declaration synx ( also class as index type)
• initalization
• size
• copy/compare
• built-in functions
• usage
• https://www.chipverify.com/systemverilog/systemverilog-associative-array
• notes/page-39

Question 16

mulidimensional AA

Answer 16

• initializtion
• indexing
• https://www.chipverify.com/systemverilog/systemverilog-associative-array

Question 17

display whole AA/dyn arr

Answer 17

• https://www.chipverify.com/systemverilog/systemverilog-associative-array

Question 18

assign design var to dyn variable

Answer 18

https://verificationacademy.com/forums/systemverilog/initializing-multidimensional-associative-array

Question 19

AA array of type dyn arr

Answer 19

https://www.chipverify.com/systemverilog/systemverilog-associative-array

Question 20

next/prev of AA

Answer 20

• function int next (ref index); Finds the smallest index whose value is greater than the given index
• function int prev (ref index); Finds the largest index whose value is smaller than the given index

module top;
  logic[7:0] aa_inst[string] = '{ "BEE" : 4, "AEE" : 5, "CEE" : 6};
  string idx; // unlike forach(arr[i]), where i need not be declared, idx need to be declared
  initial begin
    aa_inst.first(idx);
    $display("Associative array : %0p,  first_indx=%0s",aa_inst,idx);
      // output : associative array : '{"AEE":'h5, "BEE":'h4, "CEE":'h6} ,  first_indx=AEE

    $display("\n----------------------------");
	if(aa_inst.first(idx)) begin
	  do begin 
	    $display("\tUsing first,next ::  [%0s] = %0d",idx,aa_inst[idx]);
	  end while(aa_inst.next(idx));
	end
    $display("\n----------------------------");
	if(aa_inst.first(idx)) begin
	  do begin 
	    $display("\tUsing first,prev :: [%0s] = %0d",idx,aa_inst[idx]);
	  end while(aa_inst.prev(idx));
	end  
	
    $display("\n----------------------------");
	if(aa_inst.last(idx)) begin
	  do begin 
	    $display("\tUsing last,next ::  [%0s] = %0d",idx,aa_inst[idx]);
	  end while(aa_inst.next(idx));
	end
    $display("\n----------------------------");
	if(aa_inst.last(idx)) begin
	  do begin 
	    $display("\tUsing last,prev :: [%0s] = %0d",idx,aa_inst[idx]);
	  end while(aa_inst.prev(idx));
	end  
	
end
endmodule

Associative array : ‘{“AEE”:’h5, “BEE”:’h4, “CEE”:’h6} , first_indx=AEE

    Using first,next ::  [AEE] = 5
    Using first,next ::  [BEE] = 4
    Using first,next ::  [CEE] = 6

    Using first,prev :: [AEE] = 5

    Using last,next ::  [CEE] = 6

    Using last,prev :: [CEE] = 6
    Using last,prev :: [BEE] = 4
    Using last,prev :: [AEE] = 5

Question 21

reduction methods

Answer 21

• sum
• and
• or
• xor
• product

notes/page 41

Question 22

select random element in array

Answer 22

page 42