[Fwd: RE: [U-Boot-Users] Incorrect flash ids?]

[Fwd: RE: [U-Boot-Users] Incorrect flash ids?]

[Tolunay Orkun]

Well, there is no end to it. In my previous job, hardware engineer decided
to use 64bit bus for flash so we had 4 of them to make 64bit bus(MPC755).
So, the 32 bit ones is not enough to compare all 4 anyway.

Another perfectly valid (but unusual) scheme is to map 4 devices each in
byte mode. That 4 byte ID read would be different that the stored one if
you wanted to compare them bus wide.

> Because these flashes are 16bit wide and there are usually two of them
(one for high order 16bits and one for the low order 16 bits)
>
>>
>> Actually, it is 0x00180018. So, the question is why duplicate
>> the id in the high and low order 16 bits?
>>
>

[Fwd: RE: [U-Boot-Users] Incorrect flash ids?]

[Wolfgang Denk]

In message <20415.216.110.51.8.1074021611.squirrel@www.orkun.us> you wrote:
> Well, there is no end to it. In my previous job, hardware engineer decided
> to use 64bit bus for flash so we had 4 of them to make 64bit bus(MPC755).
> So, the 32 bit ones is not enough to compare all 4 anyway.

It is. You can read 64 bits in two chunks of 32 bits each.  There  is
actually  little chance that the upper and the lower half of your bus
will use different flash chips.

> Another perfectly valid (but unusual) scheme is to map 4 devices each in
> byte mode. That 4 byte ID read would be different that the stored one if
> you wanted to compare them bus wide.

No problem. I think there are boards doing exactly this.


Best regards,

Wolfgang Denk

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