[GreenKeys] shockingly basic question - Teletype Model 33 ASR

[Mike Douglas]

I guess I’m confused as to your test setup then. What is sending data to your Teletype? Is it coming from an external source other than the Teletype, or are you testing by somehow looping keyboard input from your TTY back out to the TTY printer?

Mike

>> On Feb 3, 2021, at 8:36 PM, Andy KN4UCL <kn4ucl at gmail.com> wrote:
> 
> I think I am still missing a trick or two here...I tried every combination of 8 and 7 even/odd/none/mark/space and I get no printing at all with 8 bit, but moderately bad spelling errors with 7.  See attachment below... presumably this means I have the non-parity keyboard?
> 
> thanks in advance for your thoughts!
> Andy
> 
>> On Sun, Jan 31, 2021 at 8:18 PM Mike Douglas <deramp5113 at yahoo.com> wrote:
>> If you select 8 bit with mark parity on your terminal server, you’ll probably get the 8N2 timing the Teletype requires (the mark parity bit serves as the first stop bit).
>> 
>> Mike
>> 
>>>> On Jan 31, 2021, at 7:11 PM, Andy KN4UCL <kn4ucl at gmail.com> wrote:
>>> 
>>> Thanks guys for the responses - a lot of great info for me to digest!  
>>> 
>>> My terminal server (Equinox ELS-16) allows me to define character size as 7 or 8 bits, and to set parity as NONE, ODD, EVEN, MARK or SPACE. 
>>> 
>>> I don't seem to have the ability to specifically state the number of stop bits, however.
>>> 
>>> Anyway.. I'm going to crack my Teletype open and confirm exactly what's going on.
>>> cheers!
>>> Andy 
>>> 
>>>> On Sun, Jan 31, 2021 at 5:43 PM Keith Lueck <kwlueck at swbell.net> wrote:
>>>> Jim & Wayne are spot-on, of course.  I learned the hard way that you best include the parity bit - even though the 33 doesn't give a whit about parity...  
>>>> My machine was occasionally producing errors when I was feeding it 7 N 2.  Wayne Durkee set me straight, and, viola, when I sent it 7 M 2, everything was 100% ducky.  
>>>> 
>>>> On Sunday, January 31, 2021, 03:32:30 PM CST, Jim Haynes <jhhaynes at earthlink.net> wrote:
>>>> 
>>>> 
>>>> All the 33s and 35s generate 11 unit code.  1 start bit, 7 data bits, one
>>>> bit which may be even parity or may be marking, and two stop bits.  That's
>>>> where 110 baud comes from. 100 wpm = 10 chars/sec and each char contains 
>>>> 11 bits.  The reason for two stop bits is the difficulty of making a
>>>> mechanical selector that is reliable at 100 wpm.
>>>> 
>>>>     ---
>>>> 
>>>>     "Ya can argue all ya wanna, but it's dif'rent than it was."
>>>>     "No it ain't! No it ain't!  But ya gotta know the territory."
>>>>         Meredith Willson, The Music Man
>>>> 
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> 
> <non parity keyboard.png>
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