[GreenKeys] End of line handling (was C-64)

[John Nagle]

> On Fri, 4 Sep 2015, drlegendre . wrote:
>
>> >You're right, I have never so much as put my hands on a mechanical
>> >printer the likes of an M15 - I had no idea they lacked EOL sensing /
>> >automatic CR. And since there's essentially zero flow control, the
>> >printer can't toggle a control line (like DTR) to give the carriage time
>> >to return and settle.?

Right. However, some Model 15 machines do have auto LF on CR and auto
CR at end of line.  One of my Model 15 machines has both features;
the other has neither.  That's an emergency measure; you will lose one 
character of info if the auto CR on end of line mechanism trips.
With it, you never get a pileup at the right margin.

My "baudotrss" program on SourceForge sends CR LF LTRS at the end
of each line, and you can configure additional LTRS characters if
desired.  However, CR LF should provide enough delay.  If it takes
more than two character times to return the carriage and let the
carriage return dashpot settle, the machine is out of spec.

There's also an "unshift on space" feature.  Some machines shift
to LTRS after every space.  "Baudotrss" understands carriage state
as being LTRS, FIGS, or "unknown".  After a space in FIGS mode,
it's treated as "unknown", so a LTRS  or FIGS will be put
before the next printing character, whether needed or not.

Baudotrss also has software right margin enforcement and word wrap,
which is worth adding if you have a computer in the loop.

Western Union built the first word wrap device in 1956 to drive a Model
15.  Here's the Western Union Technical Review article on it.

http://massis.lcs.mit.edu/archives/technical/western-union-tech-review/10-1/p040.htm

All relays; no electronics.

				John Nagle