EPROM vs EEPROM vs Flash EPROM: Key Differences Explained
Advertisement
This page outlines the key differences between various types of Erasable Programmable Read-Only Memory (EPROM), specifically EPROM, Electrically Erasable PROM (EEPROM), and Flash EPROM. These are all re-programmable memory types commonly used in processor-based systems. Like EPROMs, an EEPROM device is programmed by applying a high voltage to the control gate.
Specifications | EPROM | EEPROM | Flash EPROM |
---|---|---|---|
Relative Size of Cell | 1 | 3 | 1.2 to 1.3 |
Programming | By external Means | Internal | Internal |
Programming Technique | Hot electron injection | Tunnel effect | Hot electron injection |
Voltage | 12.5 V | 5 V | 12 V |
Resolution | Byte | Byte | Byte |
Time taken | < 100 µS | 5 ms | < 10 µS |
Erasing | By external means | Internal | Internal |
Erasing Technique | Ultraviolet light | Tunnel effect | Tunnel effect |
Resolution | Whole chip | Byte | Whole chip or block |
Time Taken | 15 min | 5 ms | 1 sec |
Key Differences Summarized
The table above highlights the core differences:
-
Cell Size: EEPROM cells are generally larger than EPROM and Flash EPROM cells.
-
Programming: EPROMs require external equipment for programming, while EEPROMs and Flash EPROMs can be programmed internally.
-
Programming Technique: Both EPROM and Flash EPROM utilize hot electron injection for programming, while EEPROM uses the tunnel effect.
-
Voltage: The required programming voltages vary across the three types.
-
Erasing: EPROMs are erased using ultraviolet light, requiring the entire chip to be erased at once. EEPROMs and Flash EPROMs use electrical signals (tunnel effect) for erasing.
-
Erasing Granularity: EEPROMs can erase individual bytes, while Flash EPROMs typically erase entire blocks or the whole chip. This difference impacts the speed and flexibility of data updates.
-
Erasing Time: EPROMs take significantly longer to erase than EEPROMs and Flash EPROMs due to the UV light erasure method.