Abstract: A method and circuitry for using two buffers containing video display information is shown. One buffer contains character mask or dot image information, while the other buffer has two portions, foreground and background, which store attribute information. In non-compatible write operations attribute information stored in registers is written to the attribute buffers when mask information is written to the first buffer. In compatible write operations the attribute value is written to the foreground attribute buffer and zero is written to the background buffer, while an OR'ed value of the attribute value is written to the first buffer. In non-compatible read operations the value in the first buffer may be obtained or a CRC value may be generated on the entire character cell. The CRC value can be compared with similar CRC values developed on the character mask of interest to determine if a character is present in the cell.

Abstract: A data processing system having an architecture that will allow high-speed direct device-to-device data transfers without the necessity of first detouring the data through a computer memory. The system consists of a host computer and a remote signal processing subsystem connected thereto. A Direct Device Access Bus and a plurality of data processing devices are provided. A controller associated with a Signal Processing Subsystem supervisor, selectively interconnects desired ones of a set of data processing devices via the Direct Device Access Bus to provide direct communication between the selected devices within a set. Several sets of devices can be serviced concurrently by the technique of dynamic time slot allocation.