Stored Program Decommutation Techniques

Abstract

The application of core storage elements directly in the ground station data path could add greatly to the solution of increasing telemetry input data load problems. Decommutator control information loaded into these elements at mission set up time allows complete front end control by the main processor. Indeed, more complex formats such as PCM sub-subframes could be handled, depending only on the extent and sophistication of the control routine. Prestoring FM muliplexer addresses on prescribed sequences with a selectable rate clock can provide a discriminator sampling scheme approaching the theoretical in terms of sample rates relating to signal frequencies. The data content is again only limited by the degree of sophistication of the control program. In general, these control programs are just extensions of the main processor. By using storage devices external to the processor, however, the dynamic decommutation can be performed in a fairly optimum manner without the high I/O data transfer from the computer. A second function provided by the core memory in the telemetry data stream is data identification. Particular preassigned bits stored with the control information can be attached to the telemetry data word as this word is transferred from the front end. These flag bits can be used to route the particular sample to the main processor or to display equipment for quick look purposes. Unique flag bits may also be used to key any special data handling required on that particular sample, such as attaching a time tag or selecting a special subroutine in the main processor.