1. A method of transmission of timing data via a timing stream of a data processing apparatus having active cycles and stall cycles, the data processing apparatus subject to occurrence of at least one event comprising the steps of: transmitting a bit having a first digital state in the timing stream upon an active cycle and not a stall cycle within the data processing apparatus; and transmitting at least one bit each having a second digital state opposite to the first digital state in the timing stream upon occurrence of the least one event within the data processing apparatus.