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.
(At the Computer)
(To the C64).
8 PIN MINI-DIN MALE to the Macintosh.
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) |