[U-Boot] problem with mpc837x start.S

[shawn Bai]

Thanks, Scott.
 
-Shawn

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> Date: Mon, 8 Aug 2011 15:42:38 -0500
> From: scottwood at freescale.com
> To: programassem at hotmail.com
> CC: u-boot at lists.denx.de
> Subject: Re: [U-Boot] problem with mpc837x start.S
>
> On 08/04/2011 06:37 AM, shawn Bai wrote:
> > When enlarging Nor Flash to 4GiB, the AM in OR0 is 0x0000_0, where the number of zero is 17.
> >
> > According to what is said in datasheet, if the bit value of some bit in address mask is 0,
> > then the corresponding bit in address will be masked.
> >
> > So, the higher 17 bits in address will be masked, is it right ?
> >
> > If so, the range accessed in flash is just 32KBytes from the BA in BR0.
> > Is that right ? But Not the same with what you mean.
>
> The address mask applies only to matching a chip select. Once it's been
> matched, the full address goes to the device -- minus the bits that the
> device does not implement. An bit whose address mask is zero is treated
> the same as the least-significant 15 bits.
>
> > And from what you replied before in this question, may I say the 32KBytes will repeat through 4GiB address space ? not 8MBytes ?
>
> No.
>
> > then, what is the effect of CONFIG_SYS_MONITOR_BASE in this ABSOLUTE branch as uboot comment indicates ?
>
> The effect is that the program counter contains "CONFIG_SYS_MONITOR_BASE
> + in_flash", so that when the code later shrinks the chipselect it will
> still be executing from flash.
>
> -Scott
>