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BF-548 DDR SDRAM Support

Question asked by Varun-Blackfin on Mar 16, 2013
Latest reply on Mar 18, 2013 by Andreas

Hi,

 

This is regarding support of DDR SDRAM on BF-548, i couldn't understand completely the below paragraph, at

 

Page-103 ADSP-BF54x Blackfin Processor Hardware Reference.

 

  1. The maximum size of supported DDR SDRAM is 512M bit (64M byte). Most of these memory devices can be configured as x4, x8 and x16.
  2. With x16, one memory chip is configured per “external” bank; with x8 configure two chips; and four chips with x4 configuration.
  3. Thus with x4 configuration, 64M byte x 4 = 256M byte per external bank can be supported.
  4. ADSP-BF54x processor two external banks provide      support for a maximum of 2 x 256M byte = 512M byte.

 

I have following queries, associated with it:

 

1. Why maximum size support of DDR SDRAM device is 64MB, when two external banks of 256MB are supported by blackfin?

2. Why cannot we use one 256 MB(x16) DDR SDRAM device ?

3. If we have to utilize 512MB then we will have to use 8 DDR SDRAM Device ?

4. There are two chip selects for DDR Controller in blackfin, are they for two separate external banks?

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