Nonvolatile families – which device is user-programmable but cannot be erased and reprogrammed afterward?

Introduction / Context:
Read-only memory technologies vary in how and when data is written. Recognizing which device is one-time programmable is important for cost, security, and field-update decisions. PROMs are intended for a single programming event after fabrication and then behave as fixed ROMs.

Given Data / Assumptions:

• User needs to write content once post-manufacture.
• No erasure mechanism exists in the target technology.
• Functionally read-only after programming.

Concept / Approach:
PROM (Programmable ROM) uses fuses/antifuses to permanently set bits. Once programmed, the physical change cannot be undone electrically or optically. By contrast, EPROMs can be UV-erased; EEPROMs and Flash are electrically erasable and reprogrammable. Mask ROMs are factory-set and not user-programmable at all.

Step-by-Step Solution:

Verification / Alternative check:
PROM datasheets describe “OTP” operation and lack any erase instructions, unlike EPROM/EEPROM/Flash parts.

Why Other Options Are Wrong:
Mask ROM is not programmable by the user; EPROM/EEPROM/Flash are erasable and rewritable.

Common Pitfalls:
Confusing PROM with EPROM due to similar names; the key difference is erasability.

Final Answer:
PROM