Video-Card detections is not the biggest problem, as there is a
signature on 0xC0000, telling there is a bios extension, and if this
test is not good enough, it is also possible scan for a signature or
to check default io ports as 0x3d4, etc.....
But consider, that many embedded machines have on-board or on-chip
vga (svga or sometimes also cga/mda). On this machines the vga is
not used, as the machines are mounted in racks and are only controlled
by serial console. For those machines, a vga detection is NOT the
solution.
In the first moment, I also thought, that autodetection is the only
solution. But on the other hand, if I consider, that GRUB in a
networked embedded environment can load the 'menu.lst' from the ethernet
(diskless operation, perhaps also in a normal operation !!), that
it is convinient to decide sitting on the host, if a machine should
use vga or serial line.
The discussion about haveing more than one serial line is not so
important, because in most cases the 'first' serial line is used as
console. But it isn't a problem configuring and using any port.
Another point.
There is a big advantage of using BIOS code for the serial line, as I
did in my first test-implementation. The UART is configured in a way,
that it only transmits data, if the hardware handshake lines are
asserted.
It is not possible, to change this on bios support. Also all M$ systems
use the UART in this mode. (I mean, you also must assert this handshake
lines, although 'NO HARDWARE HANDSHAKING' is configured).
So there is a problem to use both consoles (vga and serial) in parallel,
to output characters on both, and if one character comes in, that the
other of the both consoles can be disabled, or after timeout the system
boots.
For all such possibilities, a own UART handling instead of BIOS is
necessary. I also don't know, who to configure the serial line for
more than 9600baud with bios calls.
*** THIS LEADS ME TO A QUESTION ***
Question:
Is there a documentation of all BIOS calls.
My docus are very old from 8086 and 80286 system.
Is there anywhere a current one ?
Is there a docu concerning the terminal standards
ANSI, VT100, VT102, VT52
not to implement something else as the standards !
With friendly regards
Christoph Plattner
----------------------------------------------------------
private: [EMAIL PROTECTED]
company: [EMAIL PROTECTED]
