6 Sep
2016
6 Sep
'16
4:18 p.m.
On Tue, Sep 06, 2016, Paul Koning wrote:
[...]
19200? I didn't think the VT100 supported that.
You've got to be careful with that setting, even on devices that claim
to do it. When it first appeared, it was often a "just barely
possible" setting on the clock generator, with an actual bit rate off
a couple of percent from the correct value. If both ends used the
same clock generators, no problem of course. But if one end uses an
accurate one, you may get framing errors.
Is this why modems went to 14400 instead of 19200?
[...]
On the other hand, flow control issues do not result
in "garbage"
characters. The only way you'd get what looks like garbage is if
escape sequences are corrupted so a portion of that sequence is
mistaken for text. If you see garbage in a full screen editor, that
could be the reason. On the other hand, if you're just sending a
large document to the screen and you're seeing garbage, flow control
is not the cause.
Interesting. I've been trying to get a WiFi device for the Commodore
8-bits working consistently in 9600 bps mode, and have just been
assuming the garbage characters I get when I receive a screenful of text
all at once were due to buffer overruns. The garbage characters there
look like actual garbage, not like partial CSIs like [3;1m or whatever.
Earlier on there was some discussion about modern interface devices
with non-compliant "RS232" transceivers. If your RS232 output is
marginal, that could cause garbage. If the clocks are off, ditto. An
oscilloscope could be used to test both those theories.
I wonder if it's a similar sort of timing issue between my device and
the computer. I'll have to try a few computers and see if behavior
varies.
-- Eric Christopherson