Strange IEEE behaviour

Hallo allemaal,


As most of you know, I developed CBM-HD: use your PC as various 
drives for your CBM computer.
  http://www.baltissen.org/newhtm/cbmhd.htm

Today I decide to test some IEEE interfaces for the C64 in 
combination with a 8250 LP and my PC. I tested three types of 
interfaces:
1- just a 6821 and some resistor arrays.
2- 6821, 74LS245 and 7407/7417 OC buffers plus resistors.
3- 6821, 75160 and 75162, the wellknown DAMS interface

1 worked fine with one 8250LP but connecting a 4040 (from a friend) 
as well caused to crash everything. Running the PC alone didn't work 
either.

2 worked fine in combination with the 8250LP and the PC. Running the 
PC alone didn't work either as well. Asking for a directory I 
expected just a '$' but got several characters plus a '$' at the 
end. I tried several times and every time the seam string. 
One idea that the termination was to blame because the one of the 
8250LP was missing now.

3: in case of the DAMS interface the termination should be no 
problem but here the same result.

But why? If it is the termination then why goes the sending of the 
device number fine (I think) and goes it wrong when just '$' has to 
be sent?

Any ideas?  


--
   
Kind regards / Met vriendelijke groet, Ruud Baltissen
www.Baltissen.org







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