Retain data

PLCnext Technology & PLCnext Controls
1

Hi,
I have a problem with retain value in FW 2025.0.3 on RFC4072s
If I reboot the PLC the retain value is kept but it is lost at power off/on.
Has anyone else seen this problem?
Br Stefan

2

Hi Stefan, I struggled with the same issue a while ago on a different controller. The answer was fully understanding the documentation and noting that „cold starts“ reinitialize all variables: https://www.plcnext-community.net/infocenter/extended_retain_handling/
„“"
Furthermore, IEC 61131 defines three start modes:
Cold Restart

  • initializes all variables
  • Warm Restart initializes only variables which are not indicated as “RETAIN”
  • Hot Restart initializes no variables

„“"
In short, retention is ignored during a cold start, and a power cycle counts as a cold start. If you really need retention, you’ll have to use persistent storage on the underlying file system or SD card (if your controller supports this).

3

Hi,
Thanks for reply.
It would be really bad if power off/on is considered as a cold restart. The behavior is new, it was not like that in 2022 LTS version.
I hope Phoenix will come with a solution or an answer on why it happens.
Br Stefan