81EU01E-E  I/O通信模件

远程/0轨的数量取决于不同处理器可以控制的变數量。远程I/0导轨与处理器之间的通信可以通过多种方式实现，包括同轴电缆、双轴电缆、屏蔽双绞线等。如果距离比较长，需要考虑噪声抑制问题，可以采用光纤通信。并行/0模块承担了与外部系统进行信息和数据交互的重要职责，可用于扩展外围设备,如键盘、LED等简单的外部设备。-般来说，51 MCU有四个8位并行I/O端口，分别是P0、PI、 P2和P3。PO 和P2可用作公共I/0端口和数据地址端口，而P3可用作公共1/0端口，并具有其他(第二)功能。只有PI可以用作公共l/0端口。图为51单片机的外部引脚结构图。并行I/0口PO~P3是支持寻址操作的，均有一定的电流能力， 可以驱动一些外部器件,但由于PO是漏极开路输出结构，所以作为常规I/0引脚时需要加拉阻。

The number of remote/0 tracks depends on the number of variables that different processors can control. The communication between the remote I/O rail and the processor can be realized in a variety of ways, including coaxial cable, dual axis cable, shielded twisted pair, etc. If the distance is relatively long and noise suppression needs to be considered, fiber optic communication can be used. The parallel/0 module takes on important responsibilities for information and data exchange with external systems, and can be used to expand peripheral devices such as keyboards, LEDs, and other simple external devices- Generally speaking, a 51 MCU has four 8-bit parallel I/O ports, namely P0, PI, P2, and P3. PO and P2 can be used as public I/0 ports and data address ports, while P3 can be used as a public 1/0 port and has other (second) functions. Only PI can be used as a public l/0 port. The figure shows the external pin structure of the 51 microcontroller. The parallel I/O ports PO~P3 support addressing operation and have a certain current capacity, which can drive some external devices. However, due to the open drain output structure of PO, it is necessary to add a drag when used as a conventional I/O pin.