微机系统中若用4片8259A构成主、从两级中断控制逻辑,接至CPU的可屏蔽中断请求线INTR上,最多可扩展为( )级外部硬中断。
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8259A的OCW1----中断屏蔽字( )设置。
A. 在ICW之前
B. 只允许一次
C. 可允许多次
D. 仅屏蔽某中断源时
当采用( )输入操作情况下,除非计算机等待数据准备好,否则无法传送数据给计算机。
A. 无条件传送方式
B. 程序查询方式
C. 中断方式
DMA方式
There are ten sentences in this section. Beneath each sentence there are four choices or phrases marked A, B, C and D. Choose one word or phrase that best completes the sentences.Tom and Dick were both heroes, but only ________ is remembered today.
A. the later
B. the latter
C. latter
D. later