@startuml
class HSI <|-- FixedClock
class HSE <|-- FixedClock
class LSE <|-- FixedClock
class LSI <|-- FixedClock
class PLLClock {
-Clock clockSource
}
class USBClock {
-Clock clockSource
}
class SYSClock {
-Clock clockSource
}
class HClock {
-Clock clockSource
}
class PClock {
-Clock clockSource
}
Clock <|.. USBClock
Clock <|.. PLLClock 
Clock <|.. SYSClock 
Clock <|.. HClock 
Clock <|.. PClock 
@enduml