A communication method between a master and a device, the master transmits in a subcycle a received condition message (RCM) for an immediately prior subcycle, wherein the RCM is an ACK when a transmission from the device in the preceding subcycle was correctly received and the RCM is a NACK when a transmission from the device in the preceding subcycle was not correctly received, comprising: including in each transmitted condition message a current priority data acknowledgement flag (CPDAF), the CPDAF being transmitted set in each condition message for each subcycle of an offset cycle after the master correctly received in a current cycle a priority data message, the offset cycle being defined as the second and subsequent subcycles of a current cycle and the first subcycle of a next cycle, the CPDAF being transmitted as cleared otherwise.