Pack_bytes

UVM
,
1

HI,
I have a question embedded in the comment section below in the code. Any help in on how to split a packed array into 2 packed arrays would be appreciated.

class my_descriptor extends uvm_object;
  
  rand bit [511:0] my_descr;
  
  `uvm_object_utils_begin(my_descriptor)
  `uvm_field_int(my_descr, UVM_DEFAULT | UVM_PHYSICAL)
  `uvm_object_utils_end

endclass  

class my_new_sequence extends proj_base_sequence;
  
  byte unsigned desc_bytes[];
  my_descriptor cmd_desc;
  
  function new (string name = "my_new_sequence");
      super.new(name);
   endfunction : new
  
  virtual task body();
    packer = new;
    packer.big_endian = 0;
    
    void'(cmd_desc.pack_bytes(desc_bytes, packer));
    
    //desc_bytes is now a packed array of 512 bits
    //How do I split 'desc_bytes' so that I will have
    //2 packed arrays of 256bits each(desc_bytes_lo and desc_bytes_hi)?
    
     
    
  endtask  
endclass
2

In reply to Val.engg:
Use a bit-stream cast:


bit [255:0] desc_bytes_lo, desc_bytes_hi;

{desc_bytes_hi, desc_bytes_lo} = 512'(desc_bytes);
3

In reply to dave_59:
Thanks Dave.

One small issue in using the aboove mentioned solution (I should have mentioned earlier in my problem statement,my bad). I need to desc_bytes_lo, desc_bytes_hi to be of integral datatype.

Your inputs are highly appreciated. Thank you!

4

In reply to Val.engg:
Rather than letting me guess, can you show the declarations of desc_bytes_lo, desc_bytes_hi and how you want the bytes ordered.

5

In reply to dave_59:
I need to pass desc_bytes_lo, desc_bytes_hi to the following task



mem_wr(addr1, desc_bytes_lo);
mem_wr(addr2, desc_bytes_hi);


task mem_wr(input bit [39:0] ADDR,ref bit [7:0] WR_DATA[])
    
endtask

I need the bytes ordered so that I can use mem_wr task and write desc_bytes_lo and desc_bytes_hi into memory.

Pls let me know if I am not clear.

Again, thanks much for the help!

6

In reply to Val.engg:

OK, you really want me to guess. I’m going to assume the declarations are

 bit [7:0] desc_bytes_lo[], desc_bytes_hi[];

desc_bytes_lo = desc_bytes[0:255];
desc_bytes_hi = desc_bytes[256:511];

These are all dynamic unpacked arrays

7

In reply to dave_59:

Dave,
Sorry, did not quite understand your question the first time.

Here is what I want:

byte unsigned desc_bytes_lo;
byte unsigned desc_bytes_hi;

I am not sure if your earlier suggestion will work…I can try.
bit [7:0] desc_bytes_lo, desc_bytes_hi;

Would appreciate your inputs (now that I have answered your question).