ROM performance metric: The parameter “access time” (t_ac) measures how fast a ROM returns valid data after an address becomes stable. Evaluate this statement about access time being a measure of operating speed.

Introduction / Context:
Nonvolatile memories such as ROM, PROM, EPROM, and flash specify timing parameters that dictate how quickly data can be retrieved. The most cited figure is access time, often shown as tAA or tACC, which directly influences system performance.

Given Data / Assumptions:

• We consider read-only access, not programming operations.
• Access time is defined from address valid to data valid.
• System clocking and bus interfaces rely on this parameter to meet timing closure.

Concept / Approach:
Access time quantifies the delay through internal decoders, word-line/bit-line selection, and sense amplifiers until output drivers present stable data. Thus, smaller t_ac implies faster read performance. It is a primary operating-speed measure for random read operations in ROM-like devices.

Step-by-Step Solution:

Verification / Alternative check:
Datasheets specify maximum t_ac for speed grades (e.g., 70 ns, 55 ns). Lower numbers correspond to faster parts and higher sustainable bus frequencies during asynchronous reads.

Why Other Options Are Wrong:

• Incorrect: Contradicts standard timing definitions.
• Ambiguous: Setup/hold apply to synchronous buses; t_ac remains the key asynchronous speed figure.
• Valid only for SRAM: Access time is defined for ROMs as well.

Common Pitfalls:
Confusing program/erase timing with read access; ignoring output enable delays (tOE) that may further constrain sampling.

Final Answer:
Correct