There is disclosed a self-timed processor. The self-timed processor includes a plurality of functional blocks comprising null convention logic. Each of the functional blocks outputs one or more multi-rail data values. A global acknowledge tree generates a global acknowledge signal provided to all of the plurality of functional blocks. The global acknowledge signal switches to a first state when all of the multi-rail data values output from the plurality of functional blocks are in respective valid states, and the global acknowledge signal switches to a second state when all of the multi-rail data values output from the plurality of functional blocks are in a null state.