串口通信程序，通过汇编语言使用BIOS的。

代码说明：

本串行通信程序利用汇编语言通过BIOS中断调用和DOS功能调用实现PC机双机串行通信。其中，上位机和下位机串行口均为辅串口COM2（口地址为2FXH），对外用9针连接器与令一台PC机连接；BIOS通过“INT 14H”4个中断服务子程序，分别完成串口初始化编程、发送一帧数据、接受一帧数据以及测试通信线状态。本程序分为PC机串口自动测试程序（目的是测试串口好坏）和PC机全双工双机通信程序两个部分。-the serial communications procedures through the use of assembly language BIOS interrupt calls and function calls DOS PC Dual Serial Communication. Among them, PC and the next crew will be supplemented by serial port Serial COM2 (I address 2FXH) external with 9-pin connectors and enable a PC connection; through the BIOS "INT 14H," four interrupt service routines, complete serial port initialization programming, Send a data receiving a data communications test and the state line. The procedures are divided into PC serial automatic test procedure (for the purpose of testing Serial good or bad) and full-duplex PC-machine communication program two parts.