EPROM erase granularity — is the key advantage of EPROM the ability to erase a single byte independently?

Introduction / Context:
EPROM (Erasable Programmable Read-Only Memory) and EEPROM have similar-sounding names but very different erase mechanisms. EPROM devices are erased by ultraviolet (UV) light through a quartz window and the erase operation clears the entire chip at once. EEPROM and Flash enable electrical erase of bytes, words, or blocks.

Given Data / Assumptions:

• The claim is that EPROM’s advantage is single-byte erase capability.
• We consider standard UV-erasable EPROMs and OTP-EPROMs.
• Erase granularity is the focus, not program granularity (programming is byte-oriented).

Concept / Approach:
EPROM stores charge on floating gates. UV photons discharge all cells simultaneously when exposed for the specified time, returning the device to the erased (all 1s) state. No byte-level selective erase exists in EPROM. EEPROM (Electrically Erasable PROM) allows in-circuit, selective electrical erase—often at the byte or page level—without UV exposure, which is its key advantage for small updates.

Step-by-Step Solution:

Verification / Alternative check:
Look at EPROM datasheets (e.g., 27C256, 27C512): specify UV erase procedure and time; no byte erase command exists. EEPROM datasheets list byte/page erase/write commands.

Why Other Options Are Wrong:

Common Pitfalls:
Mixing programming granularity (byte writes) with erase granularity; conflating EPROM and EEPROM terminology.

Final Answer:
Incorrect — EPROM erases the whole device via UV exposure