non-volatile memory
A type of computer memory that can retain stored information even after power is removed.
non-volatile memory: data that survives when power dies
Non-volatile memory is any storage medium that preserves its contents after electrical power is cut off. Unlike dynamic RAM, which loses everything the moment a supply fails, non-volatile memory holds its state through magnetic, optical, or electronic charge mechanisms. This property makes it the foundation of all persistent data storage in industrial control systems, PLCs, embedded devices, and any equipment that must retain settings, logs, or firmware across power cycles.
The main types used in industrial settings are flash memory (including SSDs and USB storage), EEPROM (electrically erasable programmable read-only memory), and ferrite core or magnetic tape in legacy systems. Flash dominates modern applications because it offers high density, reasonable write endurance (typically 10,000 to 100,000 cycles for industrial-grade chips), and no moving parts. EEPROM is slower and smaller but offers greater write cycle longevity, making it ideal for storing a small number of calibration values or system parameters that change infrequently.
Reliability and wear considerations
Non-volatile memory in industrial environments faces real constraints. Flash memory degrades with repeated write cycles, a phenomenon called wear leveling, where the controller spreads writes across available cells to extend lifespan. Temperature extremes and electromagnetic interference can also corrupt stored data, particularly in EEPROM. A typical industrial SSD rated to 600 TBW (terabytes written) in a factory automation setup might last five to eight years under moderate use; exceeding this threshold risks silent data loss.
Industrial electronics rely on non-volatile memory for firmware storage, user-configurable parameters, event logging, and fault codes. A motor drive controller, for instance, stores calibration offsets and fault history in non-volatile memory so that diagnostics survive a power loss. Incorrect handling of write timing, uncompleted transactions during power failure, and bit-flip errors from radiation or heat can all corrupt this data and lock a machine or cause dangerous misoperation.
The term "non-volatile" distinguishes this class from volatile RAM, which is faster but requires constant power. Industrial designs typically use non-volatile memory for critical configuration and volatile RAM for active computation, mirroring the tradeoff between speed and persistence that defines the entire computing hierarchy.