STEbus 80x25 character text

This board would be a great way to add an 80-column terminal but the chip is essentially unobtainable.

An alternative chip would be the EF9345 chip, which is still available. This can produce 80 or 40 column text, and has colour capabilities. It was used in an 80-column board designed by the Dutch Acorn Atom user group, to allow CP/M programs to run. Therefore there should be some ready-made firmware for it. The master clock is 12 MHz, and the dot rate is 8 or 16 MHz, just like the BBC micros, so the pixels are not exactly square.

The EF9345 has no graphic modes - for that you would need the EF9366. There is a documented design by Rolf-Dieter Klein, written in German. It has example software in Z80 assembler and the BASIC his Z80-board, but the document scan quality is very poor and OCR fails to extract anything you could use to start recreating a source file - you'd have to read it and type it in.

SVC

The SVC video controller has all the features you need for high-speed text display. Its 80 x 25 format can use the 25th line as a non-scrolling status line, and attributes may be set for inverse video, reduced intensity and flashing, either on a screen-wide basis, or character by character using the top bit.

The SVC can generate interrupts. It can accept characters at a maximum rate of approximately 15000 per second. It produces standard RS170 composite video, separate TTL syncs and video, and operates with 50 Hz monitors.

The SVC is I/O mapped on the STEbus occupying four I/O locations.

Power Consumption:

typically 0.45A at 5V

Features:

• partial emulation of televideo 925 terminals
• compatible with Wordstar and Dbase II software packages
• several attribute modes
• comprehensive manual with example driver
• drivers available for CP/M, Concurrent DOS and OS9