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DescriptionQ862
Q862DVASIC interview problem

Randomize weighted onehot-or-zero requests

TechniquesRandomizationOnehotDistribution
DifficultyMedium
TopicConstraints
LanguageSystemVerilog
Requirements3 checkpoints
01

Problem

Randomize an 8-bit request that is onehot 80% of the time and all zero 20% of the time, with an index naming the active bit.

Example input and output

Use this case to check your interpretation
Input
randomize active with 80:20 active/inactive weighting, 8-bit req, and 3-bit idx
Output
One valid active result: idx=5, req=8'b0010_0000
Explanation

Exactly req[5] is asserted. The inactive result req=0,idx=0 and seven other active indices remain valid, so one solve is non-unique.

02

Requirements (3)

  • When active, exactly one request bit must be set.
  • When inactive, both req and idx must be zero.
  • When active, req[idx] must be the asserted bit.