System is made up of two parts of hardware and software , hardware part include ecg signal receive , enlarge and filter circuit and gather circuit two parts among them , design isa and pci two bus collection card of form separately ; software part include and can programme and run side by side 8255 interface and cpld and interface software design of ad574a , using interrupt way to design the software of data collecting , and realization of data compress , and software design of administrative system 本系统由硬件和软件两部分组成，其中硬件部分包括心电信号的接收、放大和滤波电路以及采集电路两部分，分别设计了isa和pci两种总线形式的采集卡；软件部分包括可编程并行接口8255和cpld与ad574a的接口软件设计、中断方式数据采集系统的软件设计、数据压缩以及病例管理系统的软件设计。
According to the designing requirement of relay protection , the paper analyses the bad handling ability of single a / d converters , the conflict between high speed and high precision of vfc , low precision in inside a / d of mc9s12dg256 , then brings forward the ad7890 which include multi - path switches , track / hold and a / d circuits . in addition , the traditional digital output circuit consists of parallel interfaces . photo - electricity segregation and middle relays , which are complex and low reliable 传统的开关量输出电路结构一般由并行接口、光电隔离和中间继电器组成，光祸多，电路复杂，可靠性差，我们采用mc33291作为开出接口芯片，大大提高了保护动作的可靠性，提高了驱动能力， mc33291的sp工接口也简化了开出电路，减少了pcb板面积。
