Photon correlator is kernel component of Photon Correlation Spectroscopy particle sizing instrumentation, which must calculate autocorrelation function in real time. The correlation processing can be carried out by hardware or software. Hardware implemented with photon correlator has good real-time processing ability, but the cost for hardware resource is pretty high. Software correlator is comparably cheap but not competent for real-time processing. Hardware and software photon correlator architecture is analyzed, and a novel least hardware resource real-time correlator architecture taking advantage of fast processing speed of FPGA devices and vast memory space of microprocessor is presented in this paper. In this new architecture, high speed and middle speed correlator channels are implemented in FPGA, within which counter, shift register and multiplier are built with logic resources. At sample times longer than 100μs, photon pulse count, the output of 16-bit counter in FPGA, is sent to DSP to finish correlation calculation. The 300Mhz float-point DSP chip TMS320C6713 is chosen, which can finish 256-channel calculation task in 100μs. The combination of FPGA and DSP significantly decreases the hardware cost of correlator on the premise of real-time processing, and brings great flexibility to the designing of correlator.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.