[ECOS] Newbie STPC question

[ntjunkie at boltblue dot net]

Hi,

I am currently trying to get eCos to work on an ST Microelectronics STPC.
It is pretty much an PC system on chip, with a 486 core.

I am not using a bios, but some vendor bootloader code which 'warm starts' the 
chip (DRAM refresh / peripheral initialization etc).

After initialization, the bootloader code copies and runs a secondary 
bootloader (which could be the eCos O/S if small enough to fit in the F block), 
either in protected mode or real mode. Depends on the option.

When the bootloader code copies and jumps to the secondary bootloader, it 
leaves the system in the following state:

Protected-mode:

CS: set to 8 (2nd GDT entry) with access to the whole 4GB range (base=0, 
limit=4GB, 32-bit code) 
DS, ES, SS: set to 16 (3rd GDT entry) with access to the whole 4GB range 
(base=0, limit=4GB, 32-bit data) 
ESP: set to the top of 640KB (ESP=000A0000h)

>From this setup, can I just jump to the beginning of my eCos build?
I notice that the romboot.S in (ecos/packages/hal/i386/pc/current/src) sets up 
some specific selectors. Are these mandatory for eCos?

What state should the processor be in upon entry to eCos?
Have I missed the point entirely?

Many thanks.

Martin.

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