31 May
2018
31 May
'18
4:46 a.m.
On Wed, 30 May 2018, Clem Cole wrote:
Right - you have to escape things and it is a real
mess. I have seen
some of the SI/SO/DLE stuff in mechanical systems like ticker tape. I
never saw a real 8-bit interface try to do it and succeed -- its messy
and suspect when data overruns occurs all hell break loose. By the time
of 8 bits and speed of 9.6K protocol's like UUCP, or IP over serial did
not even bother. I suspect in the old 5-bit baudot code times, it was
more popular to get a larger character set, but the speeds were much
slower (and the UART not yet invented by Gordon Bell).
Actually, the closest I've seen DLE being used was in SLIP and PPP; if you
needed to send a Frame End then it was escaped with (I think) 0xFF, and that
in turn was escaped. All it took was a finite state machine... Of course,
those links used RTS/CTS, but you had to flag the end of a frame (packet)
somehow.
-- Dave