US 8781898 A description fig1 is an overall block diagram of the system the digital front end 10 decomposes page description language and sends a number of separations of byte maps of contone video to the interface cards 12 by any means at the convenience of the dfe manufacturer the separations are assumed to be cyan magenta yellow black and one other as shown the interface 15 is between each interface card 12 and its corresponding rendering card 13 that output is then applied to the printer backplane or bus 14 for application to the print engine controller 16 as shown in fig2 the 60 line interface in this described embodiment has 32 data lines one each reset clock error line valid line request and page request lines and several power and ground lines the data line valid and error signals go from the interface card 61 to the rendering card 62 while the remainder go from the rendering cad to the interface card data transfer across the interface occurs when the page request line request and line valid signals are active the page request signal is driven active by the rendering card to indicate the start of a new page of data the line request signal is driven active by the rendering card to indicate that data transfer should commence within several clock edges following.