Why we are downloading to SDRAM in flashing mode?

Hi,

While using DNW we are giving download address as 0x3000 0000 which is the
start address of SDRAM.Why we are downloading to SDRAM in flashing mode?

And for what purpose nor flash is used as we are formatting and flashing
nand area only?

I am looking at part of a document and section 2

Mini2440 Downloader Instructions.

"The mini2440 NOR flash is used by the bootloader program and contains a
program inside the NOR memory that interfaces with your PC via the serial
and USB ports"

DNW with the bootloader (Vivi?) in NOR.  SuperVivi is the "2nd stage
bootloader" (?) and flash started at 0x30000000.

My notes also say when using uboot flash started at 0x32000000 (see the
tutorial by Forest Bao on the using the GPE distrubition).

Just for interest the Pengutronix BSP started flash at 0x31000000 and used
Barebox as the "2nd stage bootloader"(?)

The above is just my understanding, so it could be wrong.  As they all used
the same bootloader in NOR, I can not explain why the different starting
addresses. 

Your first post ... don't know why.

Hi Ayyappan,

To answer your second question first:

1. As @davef correctly mentions, the 2MB NOR flash present on the board
allows us to store the Supervivi bootloader. The S3C2440A processor
documentation and the schematics mention that the processor can boot in one
of two possible modes:

A. NOR Flash boot:
In this mode, Supervivi executes at power up. It has a USB driver to
download a kernel and root file system (via DNW utility) first into SDRAM
and then to write it into NAND flash. Once written into NAND flash, we need
a special NAND bootloader (nboot or u-boot for NAND) to boot the kernel and
load the root file system.

B. NAND Flash Boot:
Once the kernel and RFS is written into NAND flash, we can use this mode to
boot directly into the kernel. In this mode we cannot use DNW to
communicate with the host system.

2. The RAM address is required for temporary storage while downloading the
kernel/RFS before flashing by the Supervivi bootloader. It only needs to be
a valid RAM address in between 0x3000-0000 to 0x3200-0000 (64 MB)

Hope that clarifies.

Regards,

Gautam

Hi gautam,

I got clear with this. But I have another question. While flashing nor
through jtag we are giving Ram start address as 3 000 000 000. It is
confusing as it is a very high address. U can refer that in the download
instructions document. If u need that to refer I shall give the download
link later.

Hi Gautam,

Here is the link to download that file.
http://www.tkjelectronics.dk/elec/mini2440/Supervivi_Linux-WinCE_Guide.pdf

In that refer under the section Using H-JTag.

Thanks in advance.