CPLD is a programmable logic device with high density, high speed and low power consumption. A CPLD consists of a logic block, a programmable interconnect channel, and an I/O block. CPLD has the characteristics of flexible programming, high integration and development cycle, wide application range, advanced development tools, low cost of manufacture, low requirements on the designer's hardware experience. Therefore, they can realize large-scale circuit design, so they are widely used in product prototype design and product production.