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Combined with the performance characteristics of the common dial switch and LED digital tube, this paper introduces the design scheme of the decoding and control module of the seven-segment LED digital tube and 8421 dial switch, and gives the main hardware selection and algorithm realization, software simulation. The study of this module aims to achieve limited I/O port expansion using Altera company’s chip-EPM7l92, hut also solve the limitations that the common programmable parallel I/O interface chip cannot realize the function reuse, and its decoding is complex. On the basis of this, the 8421 dial switch driver and the seven-segment LED digital tube driver are organically combined together to solve the contradiction that the hardware cannot he fused together The cost is saved, and the anti-interference ability is enhanced. The module has been applied in a vacuum sputtering monitoring display system, a new type of vacuum gauge and other development projects, it is still stable and can accurate operate in the complex electromagnetic field environment. It is proved hy practice that the design scheme can drive 3 pieces of 8421 dial switch and 2 pieces of seven-segment IED digital tube at the same time, and can he extended according to the actual needs. So the drive module has high universality and reliability. [ABSTRACT FROM AUTHOR]