[GreenKeys] MC6800 [was: Distortion Testing of my AN/FGC-25]

[Don Sentz via GreenKeys]

Hi Chris,

Wow, you have quite a 6800 collection!  My -D1 board has the XC-prefix chips also. I use my -D1 as the CPU board in a homebrew chassis with a backplane that has both the EXORcisor sockets and the S-100 sockets. I use two 4Kx8 S-100 RAM boards that I ordered from S.D. Sales Co. from their ads in BYTE magazine.

In addition to the TTY interface card I have a homebrew audio cassette interface that I built from two articles in the March 1976 issue of BYTE. I wrote a report on it which is at https://www.scribd.com/doc/254645437/The-Bit-Boffer .

The TTY card connects to the user's MC6820 and the cassette interface to the MC6850, via the 40-pin flat ribbon connector on the top of the -D1 card.

Regarding my teletype set, You asked, > I'm not sure if this is causing you actual trouble with this machine communicating with another or with a computer?

The teletype set is working fine in my set-up most of the time. Occasionally the printer will mistype a character from the keyboard. It seems to happen most often right after I first power-up everything. When this happens it will do so for a short time and then usually clears up, and everything works fine after that. any mistypes of signals from the computer interface or tape reader are either much less frequent or do not happen at all. The reperforator has had only one definite mistype (or do I say mispunch ?) event that I have observed.

I was motivated to make the distortion tester because of effects I observed during the initial checkout of my TTY interface reader software a few weeks ago. If there had been no errors in my software then I never would have discovered that this glitch was happening! Isn't it funny how we learn things sometimes?

-73
-Don

--------------------------------------------
On Sat, 7/4/15, Chris Elmquist <chrise at pobox.com> wrote:

 Subject: MC6800 [was: Distortion Testing of my AN/FGC-25]
 To: "Don Sentz" <dr.sentz at yahoo.com>
 Cc: "GreenKeys" <greenkeys at mailman.qth.net>
 Date: Saturday, July 4, 2015, 12:53 PM
 
 Hi Don--
 
 Happy 4th to you too and to
 others on the list that observe and happy
 Saturday to those who don't :-)
 
 I see a lot of other great
 responses and I think everyone has converged on
 contact bounce as what you are seeing. 
 I'm not sure if this is causing
 you
 actual trouble with this machine communicating with another
 or with
 a computer?