摘要： 首先感谢 backkom大哥的点拨。。。 以下的例子是在做SDRAM读写时的一个仿真实例。 由于操作SDRAM读写时需要 双向数据端口 因此在代码中涉及到了Inout口的使用。 阅读全文

摘要： 首先让我们回顾一下tri-state logic gates，引自维基百科中的解释。 Three-state, or 3-state, logic gates are a type of logic gates that have three states of the output: high (H), low (L) and high-impedance (Z).The high-impedance state plays no role in the logic, which remains strictly binary. These devices are used on buses also known as the Data Buses of the CPU to allow multiple chips to send data. A group of three-states driving a line with a suitable control circuit is basically equivalent to a multiplexer, 阅读全文