Detection of logic transitions in a data processing system

A technique is provided for signaling to a first data processing circuit (47) that an output (35) of a second data processing circuit (31) is ready for processing by the first data processing circuit. The invention provides a digital electronic device, comprising digital circuitry having a plurality of inputs and responsive to a logic transition at one of said inputs to produce, an output after a processing time has elapsed since said input logic transition, a transition detector for detecting an occurrence of a logic transition at any of said inputs and producing a detection signal indicative of said occurrence, said transition detector including a latch circuit having an output for producing said detection signal, and a self-timed circuit connected to said latch circuit output for receiving said detection signal and, after delaying for an amount of time which approximates to said processing time, producing a done signal.