Working on a BIOS is much harder than i thought... Everytime I solve a problem, I run into the next.
Most headache makes the monitor, that resides there, where a BIOS usually is located.
The internal Chip-Selects are not that smart enough, that i can switch between 2 flash-chips in software.
I'm still not sure what to do - locating my bios at C0000 and let the monitor start it OR having some (discrete) logic, that switches flash-chips.
A BIOS started by this monitor could be very helpful, it features a nice debugger and all the stuff I need to work with this board. On the other side i have concerns about compatiblity...
For now i have 512k SRAM from 0x00000 to 0x7FFFF and I am working on "bare bones" for NASM and C (bcc/dev86). bcc is able to produce code, that has first argument always in AX, not on stack. This could be useful for implementing interrupts in C.
I still have to do this flash-stuff, but I got stuck because of the not-so-flexible CS-implementation on this MCU. I have a lot of AM29F010, two of them would give me 128kx16. Perfect for BIOS...
I found that datalight provided an embedded x86 bios that is highly configurable. But i couldn't find any sources or else.
I also found a XT-ROM with MS-DOS 3.31 on the net, but not had a look at it.
I read this:
http://www.drdos.net/documentation/romhtml/romch1.htmIt is about making a DR-DOS rom. I found a few DR-DOS releases on the internet, but not contain any of the stuff needed for this job and listed in the manual.
I assume, there was a seperate development-package or something similar....
Maybe someone could tell me more about this?