An effective and flexible data conversion controller for ink jet printing is proposed in this paper. It provides the capability of processing firing data to meet the requirements of both firing sequence and firing timing of the cartridge. This print data is arranged according to the nozzle layout of a selected print cartridge and the printing direction. Then output the arranged data to the firing driver of print cartridge. A hardware architecture is proposed to serve the needs of data conversion. It is an effective design that consists of two appointed selections of nozzle firing sequence and fixed nozzle pad mapping. Moreover, the proposed architecture provides programmable firing timing and it can be switched between black or color printing mode. The core technology of this data conversion hardware is now applied to an ASIC of ink jet fax engine by OES/ITRI.