Hierarchical Connections and Exports UVM

Posted on Edited on In

imp and port connectors are sufficient for modeling most connections, but there is third connector, export, which is used exclusively in hierarchical connections.

Normally hierarchical routing is not required. A port on an UVC monitor can be connected directly to an imp in a scoreboard by specifying full hierarchical pathname (e.g., env.agent.monitor.analysis_port). The structure of an UVC is fixed and so the user knows to look in the monitor component for the analysis ports.

However the internal hierarchy of a module UVC is more arbitrary, and it may be convenient to route all the module UVC connectors to the top level to allow use without knowledge of the internal structure.

On the initiator side

  • ports are routed up the hierarchy via other port instances

On the target side

  • only the component which defines the communication method is allowed to have an imp instance. So we need a third object to route connections up the target side hierarchy - export

The hierarchical route must be connected at each level in the direction of control flow:

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initiator.connect(target)

Connection rules are as follows:

  • port initiators can be connected to port, export or imp targets
  • export initiators can be connected to export or imp targets
  • imp cannot be connection initiator. imp is target only and is always the last connection object on a route

uvm_analysis_port

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class uvm_analysis_port # (
   	type 	T	 = 	int
) extends uvm_port_base # (uvm_tlm_if_base #(T,T))

uvm_analysis_port

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class uvm_analysis_port # (
   	type 	T	 = 	int
) extends uvm_port_base # (uvm_tlm_if_base #(T,T))

uvm_analysis_imp

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class uvm_analysis_imp #(
   	type 	T	 = 	int,
   	type 	IMP	 = 	int
) extends uvm_port_base #(uvm_tlm_if_base #(T,T))

QA

  1. What are the three distinct functions of a scoreboard?

    Reference model, expected data storage and comparison

  2. To how many consumer components can an analysis port be connected?

    Any number, including zero

  3. What are the names of the two declarations made available by the following macro:

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    `uvm_analysis_imp_decl(_possible)

    Subclass uvm_analysis_imp_possible

    Method write_possible

  4. Why should a scoreboard clone the data received by a write method?

    The write method only sends a reference, therefore if the sending component uses the same reference for every data item, overwriting of data in the storage function of the scoreboard is possible without cloning.