For example, a system has its own bus system, including 8-bit data lines, 8-bit address lines and some control lines. The application of this situation requires many chip pins and fast decoding speed, which is the strength of FPGA/CPLD. Because of its parallel characteristics, it can achieve ideal results when reading and writing RAM or doing large-scale IO processing (such as an IO card with 10 channel input).
At the same time, according to the current trend, when nios system (equivalent to ARM or MCU) becomes more and more mature and faster, we can merge a complex system into FPGA, that is, only one FPGA is used to realize most functions, which is called SOPC. This can greatly save PCB area and cost.
Plus a more professional answer:
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