If failure is detected in multiple layers, a failure detection recovery processing unit is activated simultaneously in each layer and performs operations up to immediately before switching a main signal. A communications link is provided between the data interface controller and the image processing system for synchronization by the data interface controller, of the physical document as conveyed and the virtual document image captured by the image processing system. When a NOP instruction is detected, the dispersal logic places the NOP into a no-op port for execution.