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Acorn 40 Column VDU Interface

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Acorn 40 column VDU interface front

 Acorn 40 Column VDU Interface (front)

Acorn 40 column VDU interface back

 Acorn 40 Column VDU Interface (back)

The Acorn 40 Column VDU interface is from a System 4. The part no. is 200,002 Issue3. The front pannel has a DIn socket, a phone socket and a reverse video switch.

The Visual Display Unit Controller board connects to the standard Acorn bus as used by Acorn Eurocard products. It provides a TV display for all such systems with 1K of RAM mapped on the host computer data bus. Text and Teletext graphics are transparently written onto the screen by the CPU.

The intelligent device is a 6845 VDU controller which provides all the synchronisation signals to drive a 625 line 50 fields per second VDU, together with refresh addresses for the character RAM. Characters are then fed to a SAA5050 character generator which produces the necessary dot patterns to create the characters to refresh the VDU.

The SAA5050 produces teletext characters and special effects (such as flash and double height) and has Red, Green and Blue drive outputs giving coloured text and graphics.

The card will drive a monochrome or colour tv monitor directly via RGB or composite signals, plus sync, or via an encoder and modulator will drive a colour tv. In monochrome, colours appear as shades of grey.

When this card is supplied in a system, the software drivers are incorporated in the operating system.

Here is a brochure for the Acorn VDU  card.