14 Jun
2015
14 Jun
'15
10:05 p.m.
How in hell a *cable* can result in garbage beats me. I would expect
data, or no data - not garbage data...
Two things spring to mind :
1) Open-circuit signal ground, with the ground therefore completed by mains earth. I had a
nasty
version of that years ago, the system would work with a VT100 (at lower baud rates), but
not at all
with my Tandy M100 laptop.
2) Too much stray capacitance. Given a sensible output impedance on the driver (and there
is a
specification for this), this will round off the pulses, make narrow pulses too small, and
so on. This
is the more likely cause I think. How long was the defective cable?
-tony