Remanence (automation technology)
In automation technology , remanence describes the property of operands to retain their value in the event of a power failure.
Non-retentive operands lose their memory content after a power failure.
With older PLCs , the memory area with the retentive data continues to be supplied with a buffer battery in the event of a power failure. In current PLCs, the retentive data are stored in a flash memory. In the event of a power failure, the processor is supplied for a short time by a capacitor and writes the data to the flash memory . The size of the retentive memory differs depending on the controller used. The programmer must decide on a case-by-case basis whether the information saved in this way is useful for restarting the system after a restart. In special cases, undesirable consequences are also possible.
With most PLCs, retentivity can be set for counters, times, flags and data blocks.
Retentive flags are also referred to as latching flags.
Related topics
- Programmable logic controller - device that is used to control or regulate a machine or system
- Automation technology - an interdisciplinary branch of technology and an engineering science that deals with all measures to automate machines or systems
Web links
Individual evidence
- ↑ Programming guide for S7-1200 / 1500. (PDF) In: industry.siemens.com. Siemens AG, February 1, 2019, accessed May 30, 2019 .