An asynchronous first device in communication with an asynchronous second device. The time for the first device to complete a processing cycle is a first device major frame and the first device major frame comprises a first device dedicated processing time slot at the end of the first device major frame. The first device is configured to send a rescheduling signal to the second device when it has completed a first device major frame. The first device is configured, during every first device dedicated processing slot, to: monitor for a rescheduling signal sent from the second device to the first device; and if a rescheduling signal from the second device is received: reschedule the current first device major frame to a rescheduled first device major frame; wherein the end of the rescheduled first device major frame coincides with the time the rescheduling signal from the second device was received.