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

DescriptionQ932

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Q932DVASIC interview problem

Race a transaction against a scoped watchdog

TechniquesDVSystemVerilogfork joinWatchdogTimeoutCleanup

DifficultyMedium

TopicTestbench Concurrency

LanguageSystemVerilog

Requirements4 checkpoints

Problem

Run a transaction and a timeout concurrently. Continue when either finishes, stop only the losing child, return one success-or-timeout result, and leave unrelated background processes alive.

Task headerSystemVerilog

task do_transaction();
task wait_timeout();

Example input and output

Use this case to check your interpretation

Input

transaction completes after 8 cycles; timeout would complete after 20 cycles

Output

success = 1, the timeout child is stopped, and an unrelated monitor remains alive

Explanation

The transaction branch deposits the first result token; join_any returns, and disabling only the named contenders fork removes its losing sibling.

Requirements (4)

Use join_any to detect the first completed contender.
Cancel the remaining contender before returning.
Scope disable so it cannot terminate unrelated descendants owned by the caller.
Publish exactly one success or timeout result, including when completions occur in the same time slot.