how to understand powerpc's BRx ORx

[Kumar Gala]

On Sep 10, 2010, at 12:56 AM, hacklu wrote:

> I didn't understand the address mask.
> it's said that: BR[BA] is the base address,the OR[AM] is the  address mask,
> "Provides masking for corresponding BRx bits. By masking address 
> bits independently, SDRAM devices of different size address ranges can be used. Clearing 
> bits masks the corresponding address bit. Setting bits causes the corresponding address 
> bit to be compared with the address pins. Address mask bits can be set or cleared in any 
> order, allowing a resource to reside in more than one area of the address map. SDAM can 
> be read or written at any time."
> 
> how to understand it?
> for instance, if my BR0[BA]=0111_0000_0000_0000_0, OR0[AM]=1111_1111_1111
> if I want to access the 0x70000000 or the 0x71000001.what address calculate will be taken?

Can you let us know which chip you are looking at using?  There is a bit of variation so its useful to know.

- k