我看到许多开发板的电路图上，当44b0与SDRAM连接时，地址线A21、A22和A23通过4个22欧姆的电阻，共同构成BA0和BA1，我实在想不通它的原理是什么，请知道的指点一下！当A21和A22都为高电平的时候，BA0为什么；当A21和A22都为低电平的时候，BA0为什么；当A21和A22一个为高电平，一个为低电平的时候，BA0又为什么？
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[求助]44b0与SDRAM的连接
我也听别人说过是为了扩展内存用，但我想不通它的原理！比如A21和A22都是高电平，A23是低电平的时候BA0和BA1上是怎么样的？A21和A22都是低电平，A23是低电平的时候BA0和BA1上是怎么样的？A21和A22一个是低电平，一个是高电平，A23是低电平的时候BA0和BA1上又是怎么样的？我想BA0和BA1肯定要能出现00、01、10、11四种情况才对吧，可是现在就是直接用电阻连上去，又不是逻辑门，这样的话原理是什么呢？？
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拜托哪位知道的提点提点吧！！
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这块电路是为了选择开发板上SDRAM的容量，是用8M byte的还是16M byte的
具体你要看44b0的手册里关于连接SDRAM的那一部分
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不要过于钻牛角尖了......不是所有的原理图上的电阻都非得焊到板子上的，呵呵。
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