[GreenKeys] Punch Binary Tape on an ASR33

[Paul Pennington]

Doug;

Most early microcomputers used with ASR-33 Teletypes avoided the problem by
converting each binary byte to a hexadecimal pair of characters.  That
takes more tape, but avoids your problem completely since only the numbers
0 to 9 and the letters A to F are sent.  Some schemes add an address where
the code is located, checksums, etc.

Any reference book on the Motorola 6800 explains one scheme for doing
that.  It's included in ROM on all the 6800 systems I'm familiar with, but
it would be easy to write a small program to use it on any computer.

Paul Pennington
Augusta, Georgia

On Mon, Apr 6, 2015 at 1:15 PM, Jones, Douglas W <douglas-w-jones at uiowa.edu>
wrote:

> On Apr 6, 2015, at 11:43 AM, Dave G4UGM wrote:
>
> > Is it possible to punch binary tape on an ASR33. It seems the control
> codes get interpreted and so some codes can’t be punched? What about
> reading tape?
>
> It all depends.
>
> The binary format used by the DDP 516 guaranteed that all binary
> data was "TTY Safe" -- that is, it guaranteed that nothing was
> included in the binary data that would be decoded by the stunt box
> or printed.  The net result was that it could intersperse the
> binary with the listing, neither interfering with the other even
> if both were punched on the tape (but it output the punch-on,
> punch-off control codes so the listing was not punched).
>
> More generally, take the ribbon off the TTY, roll paper around
> the platten, and then you can freely punch binary.  It will hammer
> away at your scrap paper while you punch.  A bit of wear and
> tear on the print mechanism, but no major losses.
>
>                 Doug Jones
>                 jones at cs.uiowa.edu
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