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Q029FreeDesign Verification

Unknown Output After Reset

Difficulty
Easy
Topic
Waveform Debugging
Language
SV
Interview prompt

Question

Each column shows one rising clock edge. reset_n is the top-level active-low reset, and both displayed output registers are still unknown on the first edge after release. Their local reset, out_reset_n, must clear out_valid to 0 and out_data to 0x00. The top-level and local reset paths may differ. Which signal would you trace next to check whether reset reached the output registers?

Waveform for Unknown Output After Reset. Signals: reset_n, out_valid, out_data. Numbered markers identify sampled columns.
Read the sampled columns from left to right, then test each choice against the stated timing rule.
Choose one

Answer choices

  1. A. The write-data bus.
  2. B. The FIFO full flag.
  3. C. The interrupt mask.
  4. D. out_reset_n at the reset pins of the output registers.
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