ovm_do problem()

Question

i have a problem ,when i use ovm_do to randomize my sequence_item, i also want some property like content[$] to be set equal to constant value , so i use mid_do function to set req.content[0]==* ... but it turns out to be wrong , i am confused ... help me ~~

Answer 1

kurts

Full Access

150 posts

April 16, 2010 at 3:53 pm

It's hard to tell what it wrong with the limited information that you posted.

I would recommend that you don't use ovm_do macro or mid_do.

Instead, use the function API directly. It makes debugging problems a lot easier.

In your body...

$cast(txn_handle, create_item(transaction_classname::type_id::get(), m_sequencer, "name"));
start_item(txn_handle);
// Do what you need to do to set transaction fields, randomize, etc. here
finish_item(txn_handle);

See the OVM reference for more information on create_item, start_item, and finish_item.

-Kurt

Answer 2

jojofly

Full Access

3 posts

April 18, 2010 at 6:26 pm

thanks kurts, i think i may not clearly describe my problem.
for example
class my_trans extends ovm_transaction
rand bit a;
rand bit [7:0] payload[$];
....
endclass

the class have two property ,and i can add constraint in sequence to send my_trans with a=1,

class my_seq_1 extends ovm_sequence #( my_trans)

...
task body;
`ovm_do_with(req,{req.a==1})

but how can i constraint payload to a constant array ? if in some sequence i need payload[0]=`h30,payload[1]=`h40,...

Answer 3

kurts

Full Access

150 posts

April 19, 2010 at 9:42 am

Here are two ways you could do this:

1) call rand_mode(0) on your transaction field before randomizing (e.g. txn.payload.rand_mode(0)) and then assign directly to the payload array.

2) In your constraint, use the foreach construct:

{ foreach ( payload[i] ) payload[i] == other_constant_array[i]; }

There is probably another, easier way, but these two ways are what I can think of off the top of my head.

-Kurt

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