1,000+ ASIC Interview Questions: SystemVerilog, UVM & RTL

DescriptionQ117

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Q117DVASIC interview problem

Detect missing type-priority coverage

TechniquesDVCross coverageBitmapMissing bin

DifficultyMedium

TopicFunctional Coverage

LanguageSystemVerilog

Requirements5 checkpoints

Problem

Given packets containing type, size, and priority fields, track the type-by-priority cross without built-in covergroups. Report whether every expected pair has been observed and return the first missing pair.

Class declarationSystemVerilog

class CoverageGapDetector;
  function new(int num_types, int num_prios);
  function void sample(packet_t p);
  function bit all_combinations_hit();
  function void first_missing(output int miss_type,
                              output int miss_prio);
endclass

Example input and output

Use this case to check your interpretation

Input

type_count=2, priority_count=2; sample (0,0),(0,1),(1,0)

Output

all_combinations_hit=0; first_missing=(1,1)

Explanation

Three unique pairs set three cells in the dense 2x2 domain, leaving the row-major final pair unobserved.

Requirements (5)

Validate both lower and upper bounds of the sampled type and priority values.
Count repeated observations of the same pair only once.
Implement all_combinations_hit and first_missing queries.
Use storage proportional to the declared dense domain and reject invalid constructor dimensions.
Do not use a SystemVerilog covergroup.