说明：  台湾人梁奕智写的VHDL编程学习的PPT讲义，里面包括内容有D触发器、寄存器、累加器、计数器、有限状态机等非常有用的内容。
(Taiwanese Liang-chi written in VHDL programming learning PPT lectures, which include the contents of D flip-flops, registers, accumulators, counters, finite state machine such as a very useful content.)