This is the keypoint
we have to use a P1.X as select pin because the 51 architecture only admits 64K addressable volume and provide 16 pins Address Bus( P0 and P2).As a result,the address method is complicated.For example,using P1.0 to address another 64K,when you wanna address the extended memory,you should clear P1.0 firstly,which maps the extended 64K as your based 64K .
发表时间:2004年8月19日15:15:30