Re: [ECOS] flash base mask question

[John Newlin <jnewlin at rawbw dot com>]

Gary Thomas wrote:

> On Wed, 2003-11-12 at 11:07, John Newlin wrote:
>  
>
> > In file:
> >
> > /packages/devs/flash/arm/uE250/current/include/uE250_stratflash.inl
> >
> > There is a line that says:
> >
> > #define CYGNUM_FLASH_BASE_MASK  (0xFC000000u) // 32Mb total
> >
> >
> >
> > First question:
> > Does Mb stand for Megabit or MegaByte?
> >
> >
> > If Megabyte should the number not be?
> > ~(1024*1024*32-1) which is: 0xfe00_0000  ( i wish c did underscore in
> > numbers like verilog)
> >
> >
> > If it is megaBIT then it would it not be:
> > ~(32/8*1024*1024) which is:  0xffc0_0000
> >
> >
> > Or maybe the mask is per device?  There are 2 of these 32MB devices, which
> > would then make a total of 64MB and then the mask would make sense to my
> > simple brain.
> >
> >
> > If the numbers in the file are indeed correct, can someone please explain
> > to me how to derive the mask so that I can put the correct mask for my
> > device?
> >
> >    
>
> It's MegaBytes and in this particular case, the value doesn't match the
> comment :-(
>
> The value should be ~((32*1024*1024)-1) == 0xFE000000.  It's used to 
> take an arbitrary FLASH device and divine the device base address from
> it.  It should correspond to the size of the largest device [set] which
> can be installed.
>
> Note: it's only used by the Intel FLASH device drivers in any case.
>  

Gary, thanks for the clarification, that number makes sense to me. 
We have strataflash on our board which is why I picked this as a 
template to copy from.

fis and friends are all happily working.

Thanks,

-john



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