8bit Printer Ports

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The CPC Printer Port has only 7 bit data. Which is sufficient for English 7 bit ASCII character sets, but not enough for 8 bit character sets. Also, printing bitmap graphics usually requires 8 bit data (though usually can also print 7 pixels columns combined with a reduced line-feed rate). Amstrad's DMP1 works perfectly with 7 bit, but Amstrad's later DMP2000/DMP2160 include a few functions that won't work on 7 bit ports - so even the official CPC printers aren't fully compatible with the CPC printer port.

There's a software solution though, proposed by Amstrad Computer User using a replacement driver (only for printers accepting EPSON control codes).

Internal 8 bit Printer Ports/Mods

Happy Computer 8 bit Printer Port upgrade (DIY)

A good method to upgrade to full 8 bit has been described in the german magazine "Happy Computer (Schneider Sonderheft) 2/85 and 4/86":

  • Disconnect the D7 pin from ground, and wire it to the PIOs Tape WR DATA pin instead (That is, Pin 12 of the 8255 chip).

Sharing that pin will cause no problems (as long as you do not attempt to send data to the tape drive and to printer at the same time). Of course, you will also have to customize your software, or BIOS ROM, or the BIOS jump vectors in RAM, in order to take advantage of the modification. In contrast, this DIY is supported by FutureOS.

CPC Schneider International - 8 bit Printer Port Mod

DIY from CPC Schneider International (issue 12'85, page 64), this solution uses joystick port pin 8 (or (keyboard?) pin 2, unclear?).

PC Amstrad International - 8 bit Printer Port Mod

DIY from PC Amstrad International (issue 8/9'91, page 69-70), this solution uses PPI.Pin12 (same as the Happy Computer 8bit Printer Mod).

8 bit Printer Port in KC Compact

The KC Compact uses the bit 5 of PPI Port C as 8th printer bit (this is same as the Happy Computer mod, see above). Although the 8th bit is a built-in feature, the KC Compact Firmware doesn't support it. But it's supported by FutureOS.

8 bit Printer Port in Aleste 520EX

The Aleste 520EX includes an 8bit printer port, using PSG Ext Port B for data (which does not exist on the CPC), and PPI port C, Bit 4 for strobe (which would be Tape Motor in CPC). The Aleste doesn't have the normal CPC-style Printer Port at Port EFXXh. The BIOS functions are patched accordingly; including for supporting the 8th bit (unlike the CPC Plus and KC Compact, which do not support the 8th bit in BIOS functions).

8 bit Printer Port in CPC Plus

In the CPC Plus, Bit 3 of CRTC Register 0Ch can be used as eighth printer bit. For compatibility to normal CPCs, this feature can be disabled by removing the 10 kOhm resistor R30 on the mainboard (aka R130 in the schematic). See LK Links for more info. Although the 8th bit is a built-in feature, the CPC Plus Firmware doesn't support it. However the 8 bit printer port of the CPC Plus is supported by FutureOS.

External Printer Ports

Also, reportedly, the following external hardware exists:

Other external printer-related hardware (though not 8bit related):

  • Centronics to serial 8-pin DIN Adaptor for "Gabriele 9009" daisy-wheel printer from Triumph-Adler (DIY, CPC Schneider International 12-1985, pages 88, 89)
  • KDS Printer T Switch (KDS) - allows to connect 2 printers, the desired printer can be selected via software


Software solution (only for printers that support EPSON control codes)

Written by J. G. Gribbs and published in Amstrad Computer User magazine in July of 1991.


See also