Has anybody
done it or is it possible to up the speed to at least 9600?
Is this a hardware or firmware limitation?
Since the 6402 will easily handle speeds over 4800, I _think_ the
limitation is how fast the CPU can emulate a VT100, not how fast can
the UART accept characters, so given your choices, I'd say it's a
firmware limitation.
Not necesarily. The 6402 takes external transmit and receive clocks, at
16 times the desirted baud rate. If the clock generator hardware can't go
faster than 16*4800 for some reason, then you won't get more than 4800
baud. This is probalby very easy to modify, though.
-tony