VT100's

[Paul Koning]

> On Sep 6, 2018, at 3:14 PM, Carlo Pisani via cctalk <cctalk at classiccmp.org> wrote:
> 
>>> cause it's the simplest, I guess
>> The VT100 was quite complicated compared to contemporary terminals at the
>> time of its introduction.
> 
> why do you say that?
> a vt100 terminal requires only a text VDU (video display unit) with
> hw-scrolling support, and a piece of software to support the VT100
> protocol (escape-codes decoded into action for the VDU).
> 
> in fact, my Digital VT200 comes with an ASIC chip for the VDU, while
> the software side runs on an Intel 8051 MPU that directly interfaces
> the keyboard, the VDU, and the serial line
> 
> this doesn't look complex

The work of a VT100 is quite a lot more complex than that of a VT52 (many more screen operations, and more complex control sequence parsing).  With the hardware technology available at the time, it was a pretty tough job.  Does the VT100 have a microprocessor? It may predate those.  In hardwired 7400 series logic, it isn't an easy job.

The VT1xx series successors did a number of things: eliminate expansion to simplify things, offer both basic (VT101) and extended (VT102) options in separate designs optimized for the task, and use newer designs to take advantage of the rapid evolution of available silicon.  The VT2xx series did the same thing yet again.  So the successors of the VT100 are less complex (smaller boards with less stuff), less expensive, and/or more capable (VT220 for example).

Similarly, going in the opposite direction, a VT05 does far less than a VT100 with much more hardware, because the individual components were less capable.

	paul