Analysis port connections

OVM
1

Hi,

  I've implemented the following code;

class monitor extends ovm_monitor;
ovm_analysis_port #(transaction) tx_data;
…
function void build();
tx_data = new(“tx_data”,this);
endfunction
endclass

class agent extends ovm_agent;
monitor tx_monitor;
ovm_analysis_port #(transaction) data_out_tx;
…
function void build();
tx_monitor = monitor::type_id::create::(“tx_monitor”,this);
data_out_tx = new(“data_out_tx”,this);
endfunction
function void connect();
tx_monitor.tx_data.connect(this.data_out_tx);
endfunction
endclass

While compiling the above setup; I got ERROR:“NULL pointer dereference” pointing the connect method inside the agent class.
Can anyone help me to overcome the above issue?

2

Hi,

build phase works top down, means while agent build() execute the monitor build() still didn’t execute and tx_data still didn’t instantiate.

to solve it move the connect lines to the connect phase()

function void connect();
  tx_monitor.tx_data.connect(this.data_out_tx);
endfunction : connect

Thanks,
-Nadav

3

In reply to nyutal:

I didn’t get you.

The code above shows that the connect lines are in connect phase only.

4

In reply to mahesh_424:

oops,

for some reason i didn’t see its already in connect()…

sorry,
-Nadav

5

not sure if you showed all code.
All ports connection need to connect to a “imp” port which provides the put/get/write method.
if the AGENT is your final destination, then you need to give ovm_analysis_imp instead of ovm_analysis_port, otherwise you need have
agent.ovm_analysis_port.connect(xxx.ovm_analysis_imp)
hope it helps
andrew

6

In reply to aming:

Andrew,

All ports connections need NOT connect to “imp” only. Generally it is “exp”. For the final destination, where “write” function is implemented, it is to be “imp”. Please refer

http://www.verificationacademy.com/uvm-ovm/Ovm/AnalysisPort.

Mahesh, if your problem still present, try the following.

class agent extends ovm_agent;
.......
.......
function void connect();
this.data_out_tx = tx_monitor.tx_data;
endfunction
endclass

As shown above, we can just assign the analysis port of monitor to analysis port of agent, thus not having to create the analysis port of agent again.

7

then the export you mentioned is “imp” style export.
write a test case is always better to see it.
I see below :
a.blocking_put_port.connect(b.blocking_put_export) → fail
a.blocking_put_port.connect(b.blocking_put_imp) → pass

maybe i got wrong.