各位好，小弟目前在看David E.Simon的 An Embedded Software Primer一书，遇到几个看 不懂的地方想要请教 图片1:http://imgur.com/a/6raMt 图片2:http://imgur.com/a/6XaKz 图片3:http://imgur.com/a/BLsyf 图片4:http://imgur.com/a/3jr39 Q1:请问在第1张图片中，"A READ/ line, which it pulses or strobes low when it want to get data, and a WRITE/ line, which it pulses low when it want to write data out"，strobe low是什麽意思? Q2:一样在第1张，"A clock signal input, which paces all of the work...."，pace all of the work是什麽意思? Q3: 在第2张中，我知道memory address space是什麽，就是可以拉到其他的chip然後提供 其他chip address，那它跟I/O address space差在哪里呢? 换句话说，我也可以把连到 I/O address space的chip改成连到memory address space。从这本书的内文我看不出来这 两个之间的差异。 Q4: 在第2张下面跟第3张第一句，"电路图右上角的gate that drives the memory enable signal(MEMEN/) asserts that signal low when the I/O signal and A19 are both low. This enables the memory chips in the memory address space in the range from 0x00000 to 0x7ffff"，我不懂为什麽I/O signal跟A19为LOW时(此时MEMEN/输出low) 会让memory address sapce的range为0x00000~0x7ffff Q5: 在第4张图中，"Note that since this circuit asserts DV1's chip enable signal whenever A19 and I/O are high and does not check A18 through A8, the circuit can read from or write to DV1 no matter what the values of those address signals"，请问，CPU只有A0~A15，为什麽会有到A18?还是这张图画错了，是A0~A18? --

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