Difference Between the uvm_analysis ports

Can you please help to understand the functionality and clear difference between:

1. uvm_analysis_export
2. uvm_analysis_port
3. uvm_analysis_imp

I have searched in internet, there are some explanations, like those:

But still I feel that need more explanation. Can someone help please.

2 Answers

uvm_analysis_port's are the publisher, they broadcast transactions

uvm_analysis_imp's are the subscriber, they receive transactions and call a function named 'write' in the class in which they are defined.

uvm_analysis_export's can be more confusing, they are used to expose 'imp' ports at higher level of the hierarchy. For example if you have an agent which contains a component with an analysis_imp and you want to make that 'imp' available at the agent's interface level. In this situation you declare and instantiate the analysis_export in the agent class, then in the connect_phase connect the agent's analysis_export to your internal component's analysis_imp.

Its worth noting, exports are for the subscribing side, but on the publishing side regular uvm_analysis_port's can be used in the same way. So agent's can instantiate analysis_ports and connect them to an internal component's analysis_port.

This is good because it allows you to avoid reaching down into the hierarchy when you are connecting components (which makes maintenance easier):

bad:

bus_agent.internal_monitor.packet_port.connect(checker.ref_model.packet_imp) 

good:

bus_agent.packet_port.connect(checker.packet_export) 

Its also good to become familiar with the macro uvm_analysis_imp_decl(). It allows you to use more than one analysis_imp in a component.

Advantage for this analysis port is that a user can transfer data from a single producer to multiple consumers that is not archived with help of uvm_blocking_put_port.

This thing is also explained in the figure.

Here I provides sample code to get more clarity for uvm_analysis_port.

Remember: Port connection is used to connect two or more independent component.

This image gives explanation of uvm_analysis_port

uvm_analysis_port EXAMPLE

class transaction extends uvm_sequence_item; `uvm_object_utils(transaction); rand int unsigned a; rand int unsigned b; function new(string name =""); super.new(name); endfunction endclass class producer extends uvm_component; `uvm_component_utils(producer); transaction tr_inst; uvm_analysis_port #(transaction) produce_to_consumer_p; function new(string name ="",uvm_component parent); super.new(name,parent); produce_to_consumer_p = new("produce_to_consumer_p",this); tr_inst = new("tr_inst"); endfunction task run_phase(uvm_phase phase); super.run_phase(phase); phase.raise_objection(this); // tr_inst.randomize(); `uvm_info(get_full_name(),"Write the data from PRODUCER",UVM_LOW); tr_inst.a = 10; tr_inst.b = 20; produce_to_consumer_p.write(tr_inst); phase.drop_objection(this); endtask endclass class consumer_1 extends uvm_component; `uvm_component_utils(consumer_1); uvm_analysis_imp#(transaction,consumer_1) write_imp_1; function new(string name ="",uvm_component parent); super.new(name,parent); write_imp_1 = new("write_imp_1",this); endfunction function void write(transaction tr_inst); `uvm_info(get_full_name(),"Got the data in CONSUMER_1",UVM_LOW); `uvm_info(get_full_name(),$sformatf("The value of a = %0d and b = %0d",tr_inst.a,tr_inst.b),UVM_LOW); endfunction endclass class consumer_2 extends uvm_component; `uvm_component_utils(consumer_2); uvm_analysis_imp#(transaction,consumer_2) write_imp_2; function new(string name ="",uvm_component parent); super.new(name,parent); write_imp_2 = new("write_imp_2",this); endfunction function void write(transaction tr_inst); `uvm_info(get_full_name(),"Got the data in CONSUMER_2",UVM_LOW); `uvm_info(get_full_name(),$sformatf("The value of a = %0d and b = %0d",tr_inst.a,tr_inst.b),UVM_LOW); endfunction endclass class consumer_3 extends uvm_component; `uvm_component_utils(consumer_3); uvm_analysis_imp#(transaction,consumer_3) write_imp_3; function new(string name ="",uvm_component parent); super.new(name,parent); write_imp_3 = new("write_imp_3",this); endfunction function void write(transaction tr_inst); `uvm_info(get_full_name(),"Got the data in CONSUMER_3",UVM_LOW); `uvm_info(get_full_name(),$sformatf("The value of a = %0d and b = %0d",tr_inst.a,tr_inst.b),UVM_LOW); endfunction endclass class env extends uvm_component; `uvm_component_utils(env); producer p_inst; consumer_1 c_inst_1; consumer_2 c_inst_2; consumer_3 c_inst_3; function new(string name="",uvm_component parent); super.new(name,parent); p_inst = new("p_inst",this); c_inst_1 = new("c_inst_1",this); c_inst_2 = new("c_inst_2",this); c_inst_3 = new("c_inst_3",this); endfunction function void connect(); p_inst.produce_to_consumer_p.connect(c_inst_1.write_imp_1); p_inst.produce_to_consumer_p.connect(c_inst_2.write_imp_2); p_inst.produce_to_consumer_p.connect(c_inst_3.write_imp_3); endfunction endclass module main(); env env_inst; initial begin env_inst = new("env_inst",null); run_test(); end endmodule 

Here is link which gives you more clarity for analysis port as well as uvm_port.

Link: