Mac to C64 Nullmodem

From HwB

The RS-232 standard on the C64 is a little bit strange. It uses inverted TTL level for the signals. The RS-422 ports on the Macintosh has both an inverted and non-inverted input. By using the inverted instead of non-inverted the inverted C64 level is back to normal.

Pinout

Minidin8m.png

8 PIN MINI-DIN MALE to the Macintosh.

Unknown.png

DZM 12 DREH to the C64 UserPort.

Mac C64
GND+RXD- 4+5 1+12+A+N GND
RXD+ 8 M TXD (PA2)
TXD+ 6 B+C RXD (FLAG2+PB0)
D+E RTS+DTR (PB1+PB2)

Note: Larry Anderson suggested that RXD- should not be connected. However earlier information indicated that it should be connected. Please inform us if the above connection is sufficient.

GND+RXD- 4+5 1+12+A+N GND

Contributions

Sources

  • Usenet posting in comp.sys.cbm, A very simple C64 to Macintosh serial cable by Chris Baird