UG bit ???

[placidity.master_gmail.com]

abbreviations are extremely poorly described throughout the documentation. you have to turn on the fortune-teller mode to understand what is happening. in particular, the UG bit has not been "reliably" deciphered. all documentation is "raw" and made for formality, obviously not for ease of use.

[Uwe Bonnes · Accepted solution]

Well, writing some 2 letter acronym without context is also "extremely poorly described". In the conexte of timers, it means e.g. rm0399. 40.4.6 Bit 0 UG: Update generation

[placidity.master_gmail.com]

yes, you are right, it was necessary at least to indicate where I got it.