详细介绍RS-485/422原理与区别、元件选择、参考电路、通讯规约、程序设计等方面的应用要点，以及在产品实践中总结出的一些经验、窍门-Detail the difference between theory and RS-485/422, component selection, reference circuits, communications statute, procedures for the application of design elements, as well as pr