80x25 VDU Interface Board (Enhanced)

80x25 VDU Interface Board (Enhanced) Photo

Based on the issue 4 schematic and photos of an Issue 4 board, it incorporates additional circuitry to correct the Cursor and Dot Enable signals.

Presets RV1 and RV2 are adjusted to get a 12MHz and 2MHz clock respectively (if the local oscillators are used).

Links LK7, 8, 9, 10 and 11 are normally fitted in position A to select addresses as used by Acorn System COS and DOS.

Links LK4, 5, 6, 12 and 13 depend on which CPU Board is being used:

The new links LK7, 8 and 9 are used as follows:

No other links need to be fitted for normal use.

Schematic

Bill Of Materials

Front Panel Drilling

Blank PCB

80x25 VDU Interface Board (Enhanced) PCB

 

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