RS-422通信卡的设置和程序设计

分布式测控系统中，上下位机相距较远，采用RS-422标准通信卡，改变卡内部跳接器的设置可获得数据发送／保持／接收寄存器、线路状态／控制寄存器、中断允许／识别寄存器的输入／输出地址，设计相应通信程序即能实现通信．作法是：选取1A0H至1A6H为端口地址并设置其相应功能：程序设计包括波特率因子、异步通信格式、工作方式和中断准许／屏蔽位等设置的初始化程序，及发送／接收通讯程序．

Set up and Programming of RS-422 Communication Card

Control computer is far away from controlled apparatus in distributing measurement control system. Input and output addresses of series registers were obtained by using RS-422 standard communication card and by setting up inside jump-line units, these registers are data send and retain and incepting registers, circuitry state and control registers, interrupt permission and identification registers, and so on. Communication was realized by designing correspondence communication program. Practice methods are choosing port address from 1A0H to 1A6H and setting up correspondence function. Program design includes sending and incepting communication program and initialization programs that set up baud rate coefficient, asynchronism communication format, working mode and permitting break off and shield location, etc.