Re: how to understand powerpc's BRx ORx
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____0, OR0[AM]=__ > if I want to access the 0x7000 or the 0x7101.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: * 0x7000 & OR0[AM] = 0x7000 0x7000 == BR0[BA] => CS0 active, 0x on the address bus (haven't checked the actual bus width). * 0x7101 & OR0[AM] = 0x7100 0x7100 != BR0[BA] => CS0 inactive, will check the following BR/ORs With kind regards, -- Baurzhan Ismagulov http://www.kz-easy.com/ ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: how to understand powerpc's BRx ORx
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____0, OR0[AM]=__ > if I want to access the 0x7000 or the 0x7101.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 ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
how to understand powerpc's BRx ORx
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____0, OR0[AM]=__ if I want to access the 0x7000 or the 0x7101.what address calculate will be taken? thanks all -- hacklu 2010-09-10 ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
