19 Aug
2015
19 Aug
'15
9:04 p.m.
On 08/19/2015 08:40 PM, dwight wrote:
I think the main issue is that TTL is usually a weak
pullup and a
hard pulldown. RS 232 levels are equal up and down. Putting it on the
RS232 lines could even improve signal quality because the signal is
usually poorly terminated, causing reflections. The recommended
lengths and Baud rates are intended to account for this. Usually the
line is lower impedance than the input termination, requiring the
source to absorb the reflected signal. This is why 422/485 came to
be. The impedance of the loads better match that of the termination.
My setup with a DM232A doing the level translation lights up the LEDs in
one of those inline LED line monitors just fine without any apparent
signal degradation.
--Chuck