Conventionally in performing add-on processing of a predetermined code for input image data, a memory for transferring the input image data to an add-on processor and a memory for transferring it from the add-on processor to a subsequent processor cannot be shared. This invention includes a DoEngine capable of arbitrarily controlling connection switching and simultaneous execution of a plurality of components. When image data input by a scan processor is to be stored in a memory, and a predetermined code is to be added to the image data by an image processor, the DoEngine controls accesses to the same memory by the scan processor and image processor. Accordingly, these accesses are almost simultaneously executed, and the scan processor and image processor parallel-operate.