Abstract: A run length codeword system which has a set of codewords, each codeword being one byte. The first codeword of a run is divided into a 4-bit code part and 4 bits of printing hints. The code part specifies the source of the data, and the format of the remaining bytes in the run. The remaining one or two codewords specify the number of remaining data bytes in the run, or color values.

Abstract: A method and apparatus for compressing and decompressing electronic documents, with maximum intradocument independence, and maximum flexibility in optimization of compression modes. The method includes receiving documents containing unknown combinations of a plural data types, including combinations of scanned data, computer rendered data, compressed data and/or rendering tags; dividing the received image into strips of blocks determining from the image itself, which data types are present in each block; compressing data of each data type present in each block with a compression method optimized for its data type. Scanned data may be further segmented into plural scanned data types, where each data type is compressed in said compressing data step with a compression method optimized for said scanned image data type.

Abstract: A method of improving the compression ratio of image data in the form of foreground data printed over background data by arranging both kinds of data pixels into 8 by 8 pixel blocks. All blocks that do not contain at least one pixel to be printed are deleted before compression. The deleted blocks will be entirely background pixels that will be overlaid by foreground pixels, or entirely foreground pixels that will not be printed because they are located outside of foreground masks.

Abstract: A high speed image data interface between a print server containing a page description language decomposer and an interface card, and a printer containing a rendering card and a print engine, where the interface card is physically located in the printer case and is plugged into the backplane of the printer. The interface is synchronous and carries clock, page request, line request and reset signals from the renderer, and line valid, error and data signals from the interface card. Other communications between the printer and server are carried by a telephone line or local area network. The advantage of this arrangement is that the printer manufacturer can design the printer without having to design the interface card to match the server manufacturer's requirements.

Abstract: A circuit for performing high-speed 90 and 270 degree rotations of an uncompressed image in a page buffer. The rotation is performed as the data is written into and read from the page buffer, thus requiring no additional time. A special memory mapping technique is used to make efficient use of the page buffer memory.

Abstract: A protocol for communication through a bus controller to control data transfers between a host processing platform and the data bus of a bit map printer. This protocol is optimized for a data bus which connects a number of ASIC accelerator cards in addition to the printer, disk controller, bus controller and other typical system cards. The basic data transfer cycle transfers eight data words on the bus between ASIC's, I/O devices, printer and any other devices.

Abstract: A method is described for transferring data on a digital data bus system. The bus system includes a bus having a clock line for communicating a clock signal, address lines for communicating address signals, data lines for communicating data signals, and control lines for communicating control signals. A bus controller is connected to the bus. A plurality of devices are also connected to the bus. Each device has a predetermined address. The control lines include a bus grant line for communicating a bus grant signal that permits the devices addressed by the bus controller to send or receive data signals. According to the method, the bus controller generates a bus grant signal on the bus grant line and source address and destination address signals on the address lines. The devices receive the bus grant signal and the source address and destination address signals. The devices decode the source address and destination address signals in response to the bus grant signal.

Abstract: A system for using the page buffer memory which stores the pixel map to generate the cursor in a CRT display. An unused portion of the memory is used to store a duplicate copy of the band in which the cursor is currently located, and the cursor is written into its appropriate location in this duplicate band, thus destroying the underlying image in the duplicate, but not in the original. The display is then generated by cycling through the page buffer except that the duplicate band containing the cursor, instead of the original band containing the underlying image, is displayed. After each display is generated, during the time when the scan returns from the bottom to the top of the display, if the cursor has moved since the previous display, the new band containing the cursor is created in the unused portion, and the display process is repeated.