Introduction / Context:
Decoders and combinational logic can exhibit brief hazards or glitches during input transitions because different internal paths settle at different times. System designers often apply “strobing” to mask these transients so that downstream circuits see clean outputs.
Given Data / Assumptions:
- Decoder outputs may glitch during input changes.
- A strobe (enable) signal is available, typically synchronous to the system clock.
- Outputs only need to be valid during defined sampling windows.
Concept / Approach:
Strobing means gating the decoder output with an enable signal that opens only when the inputs are guaranteed stable (for example, shortly after a clock edge when propagation delays have expired). This masks hazards without requiring internal redesign, making it a reliable practical solution alongside design-for-hazard-free logic or Gray coding.
Step-by-Step Solution:
Identify the unstable interval: input transitions to the decoder.Delay observation: hold the strobe low until inputs settle.Assert strobe: gate the output to downstream logic in the stable window.Result: visible spikes are suppressed at the observation point.
Verification / Alternative check:
Scope measurement shows hazards at the raw decoder output but not at the strobed output.
Why Other Options Are Wrong:
Incorrect: Strobing is a well-known mitigation technique.Only for asynchronous inputs: Even synchronous transitions can glitch due to unequal path delays.Only if Gray coding is used: Gray coding reduces multi-bit changes but is not required for strobing to help.
Common Pitfalls:
Failing to align the strobe with data-valid timing.Assuming strobing fixes timing violations; it only masks glitches at the observation point.
Final Answer:
Correct
Discussion & Comments