SPAD FORMATTER: THE BUFFER INTERFACE BETWEEN THE SATELLITE PREDICTION COMPUTER AND THE DISPLAY.

Abstract : The computer generates information for as many as 11 satellites each 1.1 seconds. The formatter accepts these computer output words as they are generated and, through appropriate gating and timing sequences, presents the data to the display at a rate of 30 frames per second. The formatter also contains a magnetic core memory device which permanently retains map grid symbol information and provides temporary storage for points representing a suborbital path. As an experimental device, the formatter was built in a three-bay rack cabinet with room provided for possible expansion or modification of the design. To facilitate calibration and maintenance, a rack-mounted four-channel cathode-ray oscilloscope can be connected to a circuit drawer and desired test points selected by means of rotary switches. Other circuit features permit maintenance personnel to rapidly check the performance of computer and formatter and isolate any malfunction. The formatter performed as desired. The report discusses in general the design problems common to computer driven displays and considers specifically problems encountered in designing the SPAD formatter as well as the theory of operation of the overall equipment. Alternative approaches to the digital logic design problems are presented whenever possible, and the philosophy and reasons for the particular approaches chosen for SPAD are given. (Author)