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Microprocessor reliability in coal mine monitoring applications has become increasingly important in recent years. This has been true not only for the mining industry, but the computer industry as well. Processor maintenance self-diagnostics have been commonly utilized for microcomputer systems. However, in the case of a microprocessor used in a critical monitor/control environment, small memory and little free processing time limits the use of these diagnostics on a continuous basis. In the past, maintenance diagnostics have been very exhaustive for minicomputer systems and execution time can be quite long. These were primarily used on an infrequent aperiodic basis by a maintenance technician. Normal system diagnostic tests are generally run at time of power up, and the system becomes operational only after successful completion. If diagnostic tests could occur automatically without user interference, such as when the system is not being heavily utilized, it is possible that failures could be found more quickly and without cata-strophic system failure. Solutions to these problems are presented as applied to a distributed microprocessor system used for testing mine monitor/control systems. A set of self-test algorithms for an 8085-based microprocessor is presented. Tests are performed on the CPU, ROM, RAM, 8251A USART, A/D, and D/A converters, and an 8253A interval timer. These self-test algorithms are not exhaustive but have been found to provide an adequate test of microprocessor validity on power up. Similar tests could and should be used on any underground monitor/control system as a minimum test.
Date of Publication: Jan. 1985