基于ALTERa公司FPGA芯片EP2C8Q208，嵌入MC8051 IP Core，用C语言对MC8051 IP Core进行编程，以其作为控制核心，实现系统控制。在FPGA芯片中，利用Verilog HDL语言进行编程，设计了以MC8051 IP Core为核心的控制模块、计数模块、锁存模块和LCD显示模块等几部分，实现了频率的自动测量，测量范围为0.1Hz~50MHz，测量误差0.01%。并实现测频率、周期、占空比等功能。
Nios II定制指令用户指南：With the ALTERa Nios II embedded processor, you as the system designer can accelerate time-critical software algorithms by adding custom instructions to the Nios II processor instruction set. Using custom
instructions, you can reduce a complex sequence of standard instructions to a single instruction implemented in hardware. You can use this feature for a variety of applications, for example, to optimize software inner
loops for digital signal processing (DSP), packet header processing, and computation-intensive applications. The Nios II configuration wizard,part of the Quartus® II software’s SOPC Builder, provides a graphical user interface (GUI) used to add up to 256 custom instructions to the Nios II processor.
The custom instruction logic connects directly to the Nios II arithmetic logic unit (ALU) as shown in Figure 1–1.
