Associative array declaration [int][addr][queue]

SystemVerilog
1

I am trying to declare an associative array of datatype axi transaction whose index type needs to have following information :

  1. [int] to indicate master number

  2. [addr] to lookup transaction

  3. another index - this is the part where I am not sure how to declare - for the same address, the scoreboard needs to keep track of all the data that was written. So I need a queue structure to store all wdata to the same address and need to pop out in FIFO order for comparison, but I also need the address information.

What is the best way to declare this array?

Thanks

2

In reply to UVM_learner6:

axi_trans_t array[int][addr_t][$];
3

In reply to dave_59:

Hi Dave,

Before I saw your suggestion, I tried like this. Please correct me if am wrong in my approach.

axiTransaction trans_q[$]; //a q of axi transactions that need to be stored

axiTransaction assoc_array[addr_t][$]; //an assoc array to store the q of transaction for each addr.

When the transaction came in, I did a push_back to the trans_q. And then I stored the trans_q to the associative array.

Problem I encounter is that the q is always storing only one transaction.

          trans_q.push_back(my_trans);
          assoc_array[exp_addr] = trans_q;

– is this an incorrect way of approaching the problem?

In the method you suggested, how do I assign a queue to the associative array ?

4

In reply to UVM_learner6:

You only show one push_back(), so there is only one item in the queue when you do the queue copy. You should show some more code, and exactly what you expect to see.

5

In reply to dave_59:

Ok, I will add in more code to show the example.

Could you please show me how to push a queue of axi transactions into the associative array in the method you described?

axi_trans_t array[int][addr_t][$];

6

In reply to UVM_learner6:
one at a time

array[master_number][exp_addr].push_back(my_trans);

or you can copy a queue

array[master_number][exp_addr] = existing_queue_of_axi_trans;
7

In reply to dave_59:

Oh, thank you. I tried to push _back the entire q and that got me confused.

If I want to display the queue elements in the associative array, I can only pop them out and print or is there a way to see all the data elements for a particular address in the array?

In other words, I want to access the individual fields of the axi transaction that is stored in the queue, such as axi_Trans.address, axi_Trans.ID, etc.

8

In reply to dave_59:

In reply to UVM_learner6:

axi_trans_t array[int][addr_t][$];

Dave, One basic confirmation - when we declare as above, are we declare an associative array of queues or are we declaring a queue of associative arrays? Is there a difference? I think my confusion is because I thought push_back applies only to queues and for assoc array, we always do a direct assignment.

Is there a some sort of a thumb rule that can be followed when deciding which structure can be most appropriate for which scenario? If this question is too generic to be answered, pls ignore.

9

In reply to UVM_learner6:

associative array of queue :


//associative array of queue
axi_trans_t array[int][addr_t] [$];

//OR
typedef axi_trans_t axi_trans_q[$];
axi_trans_q array[int][addr_t];

/*...... assignment ........*/
//adding one element to the queue pointed by array[master_number][exp_addr]
array[master_number][exp_addr].push_back(my_trans);

//modifying/adding the entire queue which will be pointed by array[master_number][exp_addr]
array[master_number][exp_addr] = existing_queue_of_axi_trans;

queue of associative array :


//queue of associative array
axi_trans_t array[$]  [int][addr_t];  //array name is confusing as it is queue

//OR
typedef axi_trans_t axi_trans_aa [int][addr_t];   
axi_trans_aa array[$]  ;  //array name is confusing as it is queue

/*...... assignment ........*/
axi_trans_aa axi_trans_1;
axi_trans_1[m1][addr1] = my_trans1;
axi_trans_1[m2][add2] = my_trans2;
//....
//...
array.push_back(axi_trans_1);