* how to understand powerpc's BRx ORx
@ 2010-09-10 1:53 hacklu
0 siblings, 0 replies; 4+ messages in thread
From: hacklu @ 2010-09-10 1:53 UTC (permalink / raw)
To: linux-kernel
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?
thanks all
--------------
hacklu
2010-09-10
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: how to understand powerpc's BRx ORx
2010-09-10 5:56 hacklu
2010-09-10 13:37 ` Kumar Gala
@ 2010-09-12 21:08 ` Baurzhan Ismagulov
1 sibling, 0 replies; 4+ messages in thread
From: Baurzhan Ismagulov @ 2010-09-12 21:08 UTC (permalink / raw)
To: linuxppc-dev
On Fri, Sep 10, 2010 at 01:56:08PM +0800, 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,
...
> 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?
Assuming that BR0 is set to valid, the right chip select machine is
selected, etc., my understanding of MPC885RM is:
* 0x70000000 & OR0[AM] = 0x70000000
0x70000000 == BR0[BA]
=> CS0 active, 0x0000 on the address bus (haven't checked the actual
bus width).
* 0x71000001 & OR0[AM] = 0x71000000
0x71000000 != BR0[BA]
=> CS0 inactive, will check the following BR/ORs
With kind regards,
--
Baurzhan Ismagulov
http://www.kz-easy.com/
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: how to understand powerpc's BRx ORx
2010-09-10 5:56 hacklu
@ 2010-09-10 13:37 ` Kumar Gala
2010-09-12 21:08 ` Baurzhan Ismagulov
1 sibling, 0 replies; 4+ messages in thread
From: Kumar Gala @ 2010-09-10 13:37 UTC (permalink / raw)
To: hacklu; +Cc: linuxppc-dev
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=20
> bits independently, SDRAM devices of different size address ranges can =
be used. Clearing=20
> bits masks the corresponding address bit. Setting bits causes the =
corresponding address=20
> bit to be compared with the address pins. Address mask bits can be set =
or cleared in any=20
> order, allowing a resource to reside in more than one area of the =
address map. SDAM can=20
> be read or written at any time."
>=20
> how to understand it?
> for instance, if my BR0[BA]=3D0111_0000_0000_0000_0, =
OR0[AM]=3D1111_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=
^ permalink raw reply [flat|nested] 4+ messages in thread
* how to understand powerpc's BRx ORx
@ 2010-09-10 5:56 hacklu
2010-09-10 13:37 ` Kumar Gala
2010-09-12 21:08 ` Baurzhan Ismagulov
0 siblings, 2 replies; 4+ messages in thread
From: hacklu @ 2010-09-10 5:56 UTC (permalink / raw)
To: linuxppc-dev
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?
thanks all
--------------
hacklu
2010-09-10
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2010-09-12 21:14 UTC | newest]
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2010-09-10 1:53 how to understand powerpc's BRx ORx hacklu
2010-09-10 5:56 hacklu
2010-09-10 13:37 ` Kumar Gala
2010-09-12 21:08 ` Baurzhan Ismagulov
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