A binaural spike-based sound localization system suitable for real-time attention systems of robots is presented in this work. This system uses the output spikes from a 64-channel binaural silicon cochlea. The localization algorithm implements a spike-based correlation of these output spikes that measures the interaural time differences (ITDs) between the arrival of a sound to two microphones. The algorithm continuously updates a possible distribution of ITDs in the auditory scene whenever a spike arrives from either ear of the cochlea. Experimental results show that the system can estimate an azimuth angle to below 1 deg resolution. This algorithm is computationally cheaper than conventional generalized cross-correlation methods and is quicker to respond to changes in the scene.