⚡ What is EEPROM?
EEPROM stands for:
Electrically Erasable Programmable Read-Only Memory
It is a non-volatile memory that:
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Can be electrically programmed,
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And electrically erased—at the byte level,
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Without needing special hardware like UV light.
🧠 How It Works (Simplified):
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Data is stored in floating-gate transistors, like in EPROM.
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But unlike EPROM:
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It can be erased electrically using voltage pulses.
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You can erase individual bytes, not the entire chip.
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This makes EEPROM far more flexible and practical than EPROM.
🔁 EEPROM Lifecycle:
[Blank] → Program via voltage → Use → Electrically erase (byte-by-byte) → Reprogram → Repeat (10k to 1M cycles)
🧩 Key Characteristics:
| Feature | EEPROM |
|---|---|
| 🔁 Programmable | ✅ Yes |
| 🔄 Erasable | ✅ Yes (electrically) |
| 🧠 Erase granularity | Byte-level |
| ⚡ Volatile | ❌ No |
| ⏱️ Speed | Slower than RAM, faster than EPROM |
| 🔂 Endurance | 10,000 to 1,000,000 write cycles |
📦 Real-World Use Cases:
| Device | Use |
|---|---|
| 🏠 Home appliances | Store user settings |
| 📱 Microcontrollers | Store small configuration data |
| 🏥 Medical devices | Persistent settings |
| 💾 BIOS chips (legacy) | Storing boot firmware |
| 🧪 I2C/SPI EEPROM chips | Used in sensor modules, Arduino, etc. |
✅ Advantages:
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🧽 Byte-level erase and write
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🧰 No external eraser needed
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💡 Non-volatile and persistent
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⚙️ Used in embedded and low-power systems
❌ Disadvantages:
| Limitation | Why it matters |
|---|---|
| 🐢 Slower than Flash or RAM | Not for large data |
| 🧓 Limited write cycles | Overuse can wear out the chip |
| 🔍 Low storage capacity | Typically a few KB to MB |
⚖️ EEPROM vs Others (Quick Table)
| Feature | PROM | EPROM | EEPROM | Flash |
|---|---|---|---|---|
| Writable? | Once | Yes | Yes | Yes |
| Erasable? | No | UV light | Electrically (byte-level) | Electrically (block-level) |
| Granularity | N/A | Full chip | Byte | Block |
| Rewrite Cycles | 1 | 100s | ~1M | ~100K–1M |
| Usage | Permanent data | Prototypes | Settings/configs | Storage, firmware |
🧠 Interview-Ready Definition:
EEPROM (Electrically Erasable Programmable Read-Only Memory) is a non-volatile memory that allows both byte-wise electrical erasure and reprogramming. It’s used in embedded systems to store small amounts of persistent configuration or calibration data and offers flexibility that older memory types like PROM and EPROM lack.