计算机在用于实时控制过程中,往往要求在主机在线的情况下,人为更换显示画面,人为打印、修改或输入本微机系统所未能检测的某些参数等等。实现这一目的可有两种方式:其一,沿用原主机键盘,重新定义;其二,通过编程接口片子(如CTC、PIO、SIO等)外接键盘。在软件结构上, Computer used in real-time control process, often require the host online, artificially change the display, artificially print, modify or enter the computer system failed to detect some of the parameters and so on. To achieve this goal there are two ways: First, use the original host keyboard, redefine; Second, through the programming interface chip (such as CTC, PIO, SIO, etc.) external keyboard. In the software structure,