AVL Time State

sequenceDiagram
    participant "Device Time" as SystemTime
    participant "Last saved Time" as LastValidPosition 
    participant "RTC time if RTC available" as RTC 
    participant "GNSS aka GPS time" as GNSS 
    participant "User time" as UserTime 
    autonumber
    SystemTime <- LastValidPosition : load last valid time and timestamp not older then build date
    SystemTime <- RTC : load RTC time if time valid flag and timestamp not older then build date
    ... any time ...
    SystemTime <- GNSS : load GNSS time if time and date valid and timestamp not older then build date
    RTC <- GNSS : set RTC time if time and date valid and timestamp not older then build date
    ... any time ...
    SystemTime <- UserTime : set Time via $PFAL,Sys.SetTime,dd.mm.yy,hh:mm:ss
    RTC <- UserTime : set Time via $PFAL,Sys.SetTime,dd.mm.yy,hh:mm:ss
    ... any time ...
    SystemTime -> LastValidPosition : save last Valid pos and time $PFAL,GPS.Nav.SaveLastValid

TEST

sequenceDiagram
    participant John
    participant Alice
    Alice->>John: Hello John, how are you?
    John-->>Alice: Great!