Industrial Engineer · phase 4 of 16
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.
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.
