
..



Hmmm... Sounds vaguely similar to a problem I had a long time ago when I was  
trying to use Kermit.  I was building a serial connection between my Duo 210  
and my NeXT.  I think the problem was in the handshaking.  Basically, you need  
to make sure that the handshaking protocol is the same on both sides.  A safe  
place to start is by selecting NO handshaking on either end.  One problem is  
that the Zilog serial chip seems to get permanently wedged if you talk to it  
wrong, and only a reset will clear it.  I don't know the specifics.  But this  
could be a nonlinearity that screws up your attempts at debugging the system.   
It could very well be that you are doing things right--eventually-- but one  
wrong move (like trying a bad handshaking protocol) can screw up any further  
correct actions, until the next machine reset.  I have wedged my Mac and also  
my NeXT that way.

Now I can send files back and forth between the Duo and the NeXT without any  
problem, and at pretty high speeds too.

I don't know what kind of chip the PC uses, but I think the Zilog 8530 is  
pretty standard.