# DV library classes

## Overview

The DV library classes form the base layer / framework for constructing UVM testbenches. These classes provide features (settings, methods, hooks and other constructs used in verification) that are generic enough to be reused across all testbenches.

In this doc, we will capture some of the most salient / frequently used features in extended classes. These classes are being updated frequently. So, for a more detailed understanding, please read the class definitions directly.

The DV library classes fall into 3 categories - UVM RAL (register abstraction layer), UVM agent, and UVM environment extensions.

### UVM RAL extensions

The RAL model generated using the reggen tool extend from these classes. These themselves extend from the corresponding RAL classes provided in UVM.

#### dv_base_reg_field

Currently, this class does not provide any additional features. One of the features planned for future is setting exclusion tags at the field level for the CSR suite of tests that will be extracted automatically from the Hjson-based IP CSR specification.

#### dv_base_reg

This class provides the following functions to support verification:

• gen_n_used_bits(): This function returns the actual number of bits used in the CSR (sum of all available field widths).
• get_msb_pos(): This function returns the MSB bit position of all available fields. CSR either ends at this bit (BUS_DW - 1) or has reserved / invalid bits beyond this bit.

#### dv_base_reg_block

•  build(uvm_reg_addr_t base_addr): This function is implemented as a pseudo pure virtual function (returns a fatal error if called directly). It is used for building the complete RAL model. For a polymorphic approach, the DV user can use this class handle to create the extended (IP specific) class instance and call this function to build the actual RAL model. This is exactly how it is done in dv_base_env_cfg.

#### dv_base_reg_map

Currently, this class does not provide any additional features. Having this extension provides an opportunity to add common features in future.

TODO

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