[GreenKeys] Teletype model 43 RO

[Chris Elmquist]

Mike,

I didn't see any other replies to this so thought I'd chime in.
Although I do not have an M43 I suspect that the flow control you are
discussing will not help this problem per se.

In the old days, with M33 and others, the host computer was usually
configured to send a few NUL (0x00) bytes after a CR (0x0d) to give the
carriage time to return before more printable characters were sent.
Various operating systems had settings for the number of nulls to be
sent after a carriage return as a system tuneable.  These printers
did not have any character buffering and printed the character at
the very time it was sent.

If the printer has flow control then this also usually means it has some
kind of buffering and some intelligence to manage that buffer.  The CTS
signal will go false when the buffer is getting almost full and allow
the printer to catch up before setting the CTS true again and allowing
the host to send more characters toward the printer.

I think that if the printer is buffered, then someone would have thought
about the carriage return delay time and built that into the printer
control electronics and so it would already be delaying for the carriage
return time and then getting behind and causing characters to be dropped
later if you are not using the flow control.

Since you didn't say that was the problem but instead the loss of
characters at the beginning of the line, I think you need to investigate
the mechanical aspects of the carriage and make sure that it is returning
smoothly and without anything sticking or dragging so that it does return
in the time that the electronics think it should be.

Once that is resolved, then you could use the flow control to make sure
that the computer does not get too far ahead of the printing or worse
overrun the buffer and start printing junk elsewhere on a line.

Chris N0JCF
 

On Monday (12/14/2015 at 08:38PM +0000), Michael Zahorik wrote:
> I have a Model 43 RO that I have been using with a computer for years. Recently I was experimenting with changing the line width. I run the printer at 300 baud and now when I print a long line, > 72 characters, sometimes the printer will miss the first few characters of the next line. I do not use CTS or RTS on the computer. I have them connected together so the computer will not wait if the printer is busy. I now want to make this work. I looked at the books and there is a 'Terminal Ready' line, which I think just says the printer is turned on, the cover is closed and there is no alarms. And there is a 'Send Data' line. I think this is the line I need to connect to the CTS (Clear To Send) on the computer. I didn't find an exact answer in any of the documents I have. Will this work? Will the Send Data line stop the computer should the printer be busy returning the carriage etal?? Thanks
>  Mike Zahorik (414) 254-6768

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-- 
Chris Elmquist