This chapter addresses the shortcomings of traditional communication management unit solutions in supporting multiple RS485 ports and their performance bottlenecks when processing massive amounts of data. This paper utilizes Intel's new Cyclone V SoC FPGA chip, fully leveraging the high-speed parallel processing capabilities and field-programmable advantages of FPGAs, combined with the flexible computing and control capabilities of ARM processors, to design a hardware-configurable power communication management unit system based on a heterogeneous computing architecture [8]. This chapter will discuss the basic requirements for communication management units in photovoltaic arrays, as introduced in Chapter 2, and analyze the feasibility of SoC FPGAs for photovoltaic power communication system management units, considering the inherent hardware characteristics of SoC FPGAs.

3.1 Basic Concepts of SoC FPGA The Intel Cyclone V SoC FPGA, released by Intel PSG (formerly Altera) in 2013, is a new type of SoC chip that integrates a dual-core ARM Cortex-A9 processor and FPGA logic resources on a single chip. Compared to traditional standalone ARM processors or FPGA chips, the Intel Cyclone V SoC FPGA possesses both the flexible and efficient data processing and transaction handling capabilities of an ARM processor, and the high-speed parallel processing advantages of an FPGA. Furthermore, based on their unique on-chip interconnect structure, the general-purpose logic resources on the FPGA can be configured and mapped as one or more specific function peripherals for the ARM processor, communicating via a high-speed AXI (Advanced Extensible Interface) bus up to 128 bits wide, enabling data and control command interaction [9]. Because the on-chip ARM processor is hard-wired logic with optimized layout and routing, it can operate at a higher clock frequency, thus executing more instructions per unit of time [8].

3.2 Advantages of SoC FPGA Architecture Compared to Traditional Architectures 3.2.1 Advantages of SoC FPGA Architecture Compared to Standalone Processor Architecture Before the advent of SoC FPGA architecture, typical embedded systems commonly used various processors or microcontrollers as their core, such as ARM, X86, and PowerPC. The main limitation of these processors is that the number of on-chip peripherals is fixed. Once a specific processor is chosen, the functionalities it can provide are determined. For instance, if the S3C2410 processor is selected, the chip itself has only three UART serial ports. When the system requires more than three serial ports, alternative methods must be employed for expansion, such as using various serial port expansion chips. Furthermore, because the on-chip peripheral functions of these processor chips are fixed, they only support setting their operating modes to a certain extent, making it impossible to achieve highly flexible personalized customization. For example, the S3C2410 processor's on-chip UART controller has a 16-byte FIFO buffer. However, in some high-data-volume applications where a larger FIFO capacity is desired to meet functional development requirements, the on-chip UART controller cannot fully satisfy these needs and can only be handled through software [10].

Because SoC FPGAs contain field-programmable gate arrays on the chip, corresponding logic circuits can be designed according to actual application requirements, such as a UART controller with a 256-byte FIFO. Moreover, thanks to the unique high-speed interconnect architecture between the FPGA and HPS (Hard Processor System) sections on the SoC FPGA chip, functional circuits designed on the FPGA side can be directly connected to the HPS bus, thereby being mapped as a peripheral of the HPS. The HPS can then perform read/write operations on it, which is as simple and convenient as the processor operating its own on-chip peripherals.

Compared to traditional processors with fixed hardware functions, SoC FPGAs can overcome hardware limitations, flexibly design functional circuits according to actual application needs, connect them to the processor's bus, and allow the processor to control them.

3.2.2 Advantages of SoC FPGA Architecture Compared to Standalone FPGA Systems FPGAs, as devices whose implemented logic circuit functions can be changed at any time, have inherent advantages in high-speed parallel data processing. Because FPGAs implement hardware logic functions, their execution efficiency is much higher compared to processors that implement functions using program instructions. For example, to perform a multiply-accumulate operation on three data points, an FPGA can use two multipliers and one adder to complete the operation and output the result within a single clock cycle. A CPU, however, might need to break this operation into one multiply-accumulate instruction and one multiplication instruction, requiring two instruction cycles even for a high-performance CPU. At the same time, FPGAs can also implement numerous identical functions on a single chip through function replication. For instance, after designing a high-speed data acquisition + FIR digital filtering functional module, it can be instantiated multiple times to realize a high-speed multi-channel data acquisition and processing system.

However, systems designed with standalone FPGAs also have their drawbacks. Since FPGA functions are implemented through fixed logic circuits, it becomes significantly difficult to implement flexible control, human-machine interaction, or complex Ethernet protocol communication using FPGAs. Even if a complex state machine can barely achieve the functionality, it faces issues of fixed functionality and high modification difficulty. For example, in the aforementioned multi-channel acquisition system, when there is a need to plot the acquired multi-channel data as waveforms on an LCD screen or transmit it to a remote server using the TCP/IP protocol, a standalone FPGA would struggle to perform adequately. In contrast, ARM processors