LPC3250的nor flash地址线接法

以前接触过2410的片子，这个片子接SST39VF1601片子时候，A0是不用的，很容易理解，因为SST这个片子是16bit的，无需字节寻址，所以A0不用。

最近看到YL-LPC3250的板子在nor flash的接法上面有所不同，他们使用了同样型号的nor flash片子。但是他们却使用了A0地址，觉得很奇怪。查了手册，发现3250这个片子的EMC和三星2410的区别很大。

 

三星要求8bit，16bit，32bit存储器错位接线：

 

 

而3250用寄存器控制错位

 

Memory Width
When using a system that implements 8-bit static memory,
address signals A[23:0] are mapped in a 1:1 correspondence
with pins A[23:0], since transactions occur on byte boundaries.
This is done automatically by hardware in the EMC controller
when the value of MW is set to 0x0.
When using a system that implements 16-bit static memory,
address signals A[23:1] are right-justified by one bit and output
on the physical address pins A[22:0]. Address signal A0 is not
necessary because all transactions occur on half-word
boundaries. Address pin A23 is not used because the address
space available for each CSn is 16 MB. This is done
automatically by hardware in the EMC controller when the value
of MW is set to 0x1.
When using a system that implements 32-bit static memory,
address signals A[23:2] are right-justified by two bits and output
on the physical address pins A[21:0]. Address signals A0 and A1
are not necessary because all transactions occur on word
boundaries. Address pins A23 and A22 are not used because
the address space available for each CSn is 16 MB. This is done
automatically by hardware in the EMC controller when the value
of MW is set to 0x2.
00 = 8 bit.
01 = 16 bit.
10 = 32 bit (POR reset value).
11 = Reserved.

 

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http://blog.csdn.net/cgipro/article/details/6286461