The digital integrated circuit logical functional tester is needed from the design and production phases of the integrated circuits to the utilization phase of them. Usually, in the design and production stage it is used to verify the design and to discriminate the defected circuits in the production line go/nogo type tests. In these phases, AC and DC parameter tests are usually accompanied to the logical functional tests. However, in the utilization phase, no parameter tests are performed. The logical functional tests are performed to validate the logical function of the circuit or to diagnose the faulty circuit in order to replace it with a fault free circuit. Therefore the digital integrated circuit test may be frequently utilized during the entire span of the digital integrated circuits life. In this dissertation, a simple digital integrated circuit test system is developed around a microprocessor. This system performs logical functional tests on the integrated circuits. Specific microprocessor chosen is Intel 8080, 9-bit CPU chip. This single CPU chip executes various Input/Output instructions to apply test patterns to device under test and to gather result back into memory. Furthermore, this microprocessor does much software fault diagnosis to locate faulty pins and to show the error type.