An 8bit Printer Port DIY extension from german magizine CPC Schneider International (issue 12'85, page 64). Connects Printer Bit7 to Joystick1 Select signal (joystick port pin8).
This solution isn't too recommened. Some drawbacks and problems are:
- Joystick Select is an open-collector output, so HIGH levels may be unstable (this could be fixed by an additional pull-up resistor).
- Bit7 may tend to be HIGH by default, so printing normal text won't work with normal software that doesn't support the mod (the schematic includes a switch to disable the mod manually).
The circuit can be connected internally to the mainboard, or externally to the joystick/printer port connectors.
Original Article
Note
Some years later the same magazine (renamed to PC Amstrad International, issue 8/9'91, page 69) released another 8bit printer mod: This newer (and better) solution uses PPI.Pin12 (same as the Happy Computer 8bit Printer Mod).