[U-Boot-Users] RAM mapping repeats

Antonio Di Bacco antonio.dibacco at aruba.it
Wed May 10 20:59:10 CEST 2006

If I set the value you advice, I don't receive a bus error or an error 
accessing memory over the physical range ( 0x1000000 ). 


On Wednesday 10 May 2006 11:55, Joao, Nuno (ext) wrote:
> > On Behalf Of Antonio Di Bacco
> > Sent: terça-feira, 9 de Maio de 2006 21:49
> > Subject: [U-Boot-Users] RAM mapping repeats
> >
> > I have 16MB of RAM (0x01000000) then I specified BR2=0x0000xxxx and
> > OR2=0xFE000000 . Obviously if I write at 1000000 is the same as I write
> > at 0x00000000. That is, the memory repeats in the space address. This
> > doesn't seem good to me because I will not receive any bus error if go to
> > an address higher than my RAM size. Am I wrong?
> 	No, you are not wrong.
> 	You should set the CS address range only for the address range
> 	supported by your device. If you setup a bigger address range in
> 	the CS, the wrap-around happens, it is "normal" because your device
> 	is "looking" only at the less significant 24 address lines. An
> 	address like 1000000 uses more than 24 address bits, so the extra
> 	bits will be ignored because they are not connnected to your device
> 	(this is simplistic view, assuming the device has an 8 bit port size).
> 	In your case you should set AM to 1111.1111.0000.0, check your
> 	device's datasheet.
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