Wednesday, December 12, 2012

UVM Questions - 5

Q. In the accellera's UVM User guide, there are two monitors shown one at the agent level and another at the environment level, why ?
                                     Picture Courtesy- Accellera

A: There are variety of reasons why you need Monitor at different levels

    Any agent monitor also has a collector inside which collects only that data from DUT interfaces and forms a transaction which is destined to that particular agent.  As shown in the above diagram, Monitor will also have a UVM analysis ports to pass the transaction to other components in the environment like Scoreboard.

   However, the Monitor at the environment level (called as 'bus monitor' here) also snoops the DUT interface and forms the transactions destined to any master/slave agent on the bus but it won't pass the transactions to other components of the environment like scoreboard. This bus-level monitor uses those transactions to perform checking and coverage for the activities that are not necessarily related to a single agent.

Bus monitor is very useful for debugging at the SOC top level testbench environment where both source and destination of data flow (transactions) are within DUT itself. 

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