Hardware Help with diskonchip?
dwmw2 at infradead.org
Mon Dec 8 05:25:27 EST 2003
On Mon, 2003-12-08 at 05:15 +0000, Devi Priya wrote:
> In the application note (AP044) from Msystems it is given as:
> "The DiskOnChip Millennium is mapped into an 8KB memory window in the host
> memory map. This 8KB window consists of four 2KB windows." Why is this
> mapping done?
The Millennium only uses a handful of those registers. There's no real
need for the 2KiB range to be repeated -- I don't really know why it's
> Is this mapping done in hardware? I use diskonchip millennium (8MByte
> MD2800). Then shouldn't the entire 8MB shall be mapped in hardware to the
> physical address space?
You can't map 8MiB into 8KiB of physical space, even if it were NOR
flash and linearly accessible, which it's not.
> The steps for BIOS is summarised as
> 1. After DiskOnChip Millennium BUSY# signal is negated, the CPU fetches the
> Reset Vector from
> the Boot-Block area, fetches the Boot Code stored there, and starts to
> execute the code.
> 2. Boot Code runs the first part of BIOS, initializing the basic hardware
> 3. Boot Codes loads the rest of the BIOS from the flash memory to the DRAM,
> and transfer control
> (jumps) there.
> 4. Chip Select of DiskOnChip Millennium is remapped from Reset Vector to
> BIOS expansion area.
> 5. CPU executes the rest of the BIOS code, including ROM expansion devices
> (among them, the
> DiskOnChip Millennium itself).
> 6. CPU calls OS bootstrap loader (INT19).
> 7. OS is loaded, and recognizes the DiskOnChip Millennium as the boot
> 8. OS loads the application code from the DiskOnChip Millennium and executes
> 9. Application software uses DiskOnChip Millennium exactly as if it were
> using a regular hard
> In step 4 why is this remapping done? Is this mapping done in hardware?
I don't know why it's done. Probably to preserve software compatibility
with their 1980s PC BIOS extension hack, so you put your own system BIOS
into the Millennium but keep it _separate_ from their BIOS extension
which your BIOS is supposed to load later. You'd need chipset support
for changing the physical address at which the DiskOnChip appears.
> In my setup, the diskonchip is mapped in hardware to the higher order
> (0xFFFFFFFF-0xFF800000). SDRAM mapped to lower address
> (0x00000000-0x1FFFFFF). What else
> modification do i require in HARDWARE to use diskonchip millennium?
Probably none. See LinuxBIOS.
More information about the linux-mtd