positive1.puml

@startuml
participant PLC
participant Receiver
participant Buffer
participant Sender
actor Requester
hnote across:Syncronous 
PLC -> Receiver : Regular data
Receiver -> Buffer : New event
hnote across:Asyncronous 
Requester -> Sender : IsNewData?
Sender -> Buffer : IsNewData?
Buffer -> Sender : New data
Sender -> Requester : New data

@endumls