aiiadict@gmail.com wrote:
On Nov 2, 1:11 pm, Steven Hirsch <snhir...@gmail.com> wrote:ISTR that the Videx gets spoken to over hardware registers and has no relationship at all with the on-board apple video or its allocated memory region.Videx is a "terminal" device. You send it characters through the Cx00 space. It doesn't have anything to do with the video circuits on the II motherboard. It's kind of like a printer card that prints to a CRT instead of paper copy.
Right. My point was that at the hardware level it has nothing in common with the motherboard video.
The Videx Videoterm and Ultraterm bus interfaces were actually bidirectional. I wrote a driver for use with a CP/M application called BackGrounder II that supported a limited form of task switching. It was able to save and restore the text screen - even in the high-density text modes of the Ultraterm.
Steve