how to understand powerpc's BRx ORx
galak at kernel.crashing.org
Fri Sep 10 23:37:42 EST 2010
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.
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