[TUHS] Serial Interfaces (was ^T and Top)

Dave Horsfall dave at horsfall.org
Thu May 31 08:46:46 AEST 2018

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)

-- Dave

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