本设备还可用于引起使用者的注意、命令计算机读出一段文字或向电视等外部设备发出指令。
The device can also be used to attract a minder's attention, to get a computer to read out a text or to send commands to external devices such as a TV.
在读操作中，如果发出了这个指令，那么两个时钟周期后，读出数据无效，数据总线进入高阻状态。
During a READ operation, When this command is issued, data outputs are disabled and become high impedance after two clock delay.
当处理器执行一段程序时，它先从内存中读出一条指令并对它进行解码。
As the processor executes a program it reads an instruction from memory and decodes it.
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