监控程序（Monitor）的主要功能是对应用系统硬件及底层软件进行调试，也称为Debug程序，是最基本的调试工具。MC9S12DG128的Flash有128K，RAM有8K，而监控程序源代码占用不到3K FLASH，占用23字节RAM。这对用户程序的空间影响并不大。异步串行口是要用来做与PC通讯服务的，监控程序可以用，应用程序当然也可以使用。 -Monitoring Program (Monitor) of the main functions of the system on the application of the underlying hardware and software debugging, also known as Debug procedures, is the most basic debug tools. Flash has MC9S12DG128 the 128K, RAM has 8K, while the monitoring program source code occupy less than 3K FLASH, occupy 23 bytes RAM. This user program space is not too great. Asynchronous serial port is used to do with the PC communication services, monitoring procedures can be used, the application of course, can also be used.