Industrial Engineer · phase 4 of 16 · noun
Nonretentive Memory
Memory or instruction state that returns to its defined initial condition after specified resets or power cycles.
The Explain card
- Plain English
- Nonretentive memory goes back to its starting value after a power cycle or a mode change. Whatever was in it is discarded.
- Example
- A timer's accumulated value in most platforms resets when its rung goes false and again on power up. A one shot's memory bit does the same.
- Why it matters
- A fresh start is exactly what you want for in progress state that would be wrong after an outage. It is exactly wrong for anything an operator entered, so the two kinds of data should never share a tag.
- Hook
- Starts over every time.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
During commissioning, the engineer assigns the conveyor run command to Nonretentive Memory so the PLC startup sequence begins with a cleared command.
Why these words
- nonretentive English non- plus retentive, ultimately from Latin retinere, to hold back modifies the head noun by negating retentive
- memory Latin memoria, remembrance, through Old French memoire serves as the head noun naming the storage class
Where it came from
- Origin
- An English technical compound built from nonretentive and memory, with both elements ultimately derived from Latin
- Entered the language
- 20th century
- What changed
- Retentive moved from a general capacity for holding to an engineering modifier for stored state, while non- formed its technical contrast.
How it is spelled
- Pattern
- The prefix non- is written closed to retentive.
- Pattern
- The adjective keeps the suffix -ive before the noun memory.
Spelled like
- nonvolatile memory
- nonconductive material
- nonprogrammable controller
Broken into chunks
-
non
- nonvolatile
- nonconductive
-
tent
- retention
- detention
-
ive
- preventive
- responsive
-
memor
- memorize
- memorial
What it sits beside
Same subject
- retentive memory
- PLC tag
- first-scan bit
- power cycle
- startup routine
Same shape
- nonvolatile memory
- nonretentive timer
- nonisolated input
PLC memory behavior
- retentive memory
- nonretentive memory
IEC 61131-3 variable qualifiers
- RETAIN
- NON_RETAIN
Where it sits in the deck
Phase 4: PLC Memory, Tags, and Instructions
The data a program moves and the instructions that move it, from a single true or false value up to a structured array.
