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

DescriptionQ502

Q502DVASIC interview problem

Enforce a rolling bandwidth limit

TechniquesPythonSliding windowBandwidthDeque

DifficultyMedium

TopicReference Models

LanguagePython

Requirements4 checkpoints

Implement a checker allowing at most five accepted packets in any rolling ten-cycle window.

Use this case to check your interpretation

Input

accepted packet cycles=[0,1,2,3,4]; attempt at cycle 9; attempt at cycle 10

Output

cycle 9 packet rejected as sixth in the rolling window; cycle 10 packet accepted after cycle 0 expires

Explanation

Before checking cycle 10, events at or before 0 leave the ten-cycle window; the rejected cycle-9 event never pollutes legal state.

Accept monotonically nondecreasing cycle numbers.
Before checking a new packet at cycle c, remove events at or before c - 10.
Reject a sixth in-window packet without adding the illegal event to legal model state.
Use cycle counts rather than simulator time units.