[Simh] Hacking the VT100

[Bob Supnik]

The expansion capability of the VT100 was used for all kinds of 
interesting purposes.

The T11 (the one-chip micro intended to replace the LSI11 and F11 in 
embedded applications) didn't generate a lot of buzz inside DEC, so the 
team sponsored a "design contest" to spur usage. I'd never done any 
logic design in my life, so I decided to try designing a T11-based 
single board micro on a VT100-compatible expansion board. It had a 
built-in controller for the standard floppies of the day and was 
intended as a lower-cost, faster, and more integrated version of the 
PDT-11/150. A friendly hardware designer corrected the schematics, 
fabricated a breadboard, and got it running, but that's as far as it went.

The T11 sold in very large quantities as embedded controller. It powered 
the Atari "Paper Boy" arcade game and the ubiquitous RQDX3 Qbus MSCP 
controller, among other uses.

/Bob

On 7/21/2017 12:00 PM, simh-request at trailing-edge.com wrote:
> The VT100 architecture allows expansion boards to intercept the host
> communication stream by plugging into the "standard terminal port"
> (STP) connector.  This routes signals from the RS-232 (EIA) connector
> on the back of the terminal through the STP and then into the UART on
> the terminal controller board.  This lets an add-on device intercept
> ESC sequences from the host for processing by the add-on device before
> they are sent to the VT100.  The add-on device can also generate
> responses to the host in the same way.
>
> You can read more about this in Chaper 7 of the VT100 Technical Manual
> <http://manx-docs.org/details.php/1,4071>