早期的城市轨道交通车辆一般由硬线控制，没有网络或者网络不参与控制。

At the earlier stages, the vehicles were controlled by hard track lines without any network operation.

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文中主要介绍了RISC微处理器设计遵循的一般原则，RISC模型机的内部结构设计原理及硬联线控制器的VHDL软件设计方法。

This paper mainly introduces the common principles of RISC microprocessors design and the internal structure, and the way to program the VHDL software of hardwired control unit.

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