在计算机系统中,CPU响应外设有三种方法:①查询法:CPU不停地扫描外设,看相应标识位有没有置位,如果有则表明外设已经发送了数据,等待CPU处理。查询法需将进程置于死等状态,会耗费大量CPU资源,仅适合于功能单一,任务量不大的系统。②中断法:当外设发送完数据后产生中断,通知CPU来读取数据。这种方法的效率明显高于查询法,但每次中断CPU都要进行保存断点和恢复断点的操作,如果外设发送数据的间隔小于这一时间,就会造成数据丢失。中断法适合外设通信不太频繁,软件功能较多的情况。③ In the computer system, the CPU responds to peripherals in three ways: ① query method: CPU constantly scan peripherals to see if the corresponding flag bit is set, if there is that the peripheral has sent the data, waiting for CPU processing. Query method needs to put the process in the dead state, will spend a lot of CPU resources, only suitable for a single function, the task is not a small amount of system. ② interrupt method: When the peripheral sends an interrupt after the completion of the data to inform the CPU to read the data. The efficiency of this method is significantly higher than the query method, but each interrupt CPU to save the breakpoint and restore the breakpoint operation, peripherals send data less than the interval, it will result in data loss. Interrupt method suitable for peripheral communication is not frequent, more software features. ③