25 PIN D-SUB MALE to the PC
DZM 12 DREH to the C64 UserPort.
64net is a hobbyist parallel cable, first released in late 1993, that connects a Commodore 64 to a PC so the C64 can mount PC hard-drive directories as if they were local drives. The C64 side uses the 24-pin DZM 12 DREH card-edge User Port, whose data lines PB0–PB7 are driven by Port B of CIA #2 (MOS 6526) at I/O address $DD01. Three lines (PB0–PB2) run as outputs to the PC’s printer-status inputs, while five lines (PB3–PB7) read back data from the PC’s SPP data bus. The PC side uses a standard 25-pin D-sub male connector wired to the printer port’s data and status lines.
| C64 | Dir | PC | ||
|---|---|---|---|---|
| GND | A | —— | 25 | GND |
| PB0 | C | OUT | 10 | /ACK |
| PB1 | D | OUT | 11 | BUSY |
| PB2 | E | OUT | 12 | PE |
| PB3 | F | IN | 5 | D3 |
| PB4 | H | IN | 6 | D4 |
| PB5 | J | IN | 7 | D5 |
| PB6 | K | IN | 8 | D6 |
| PB7 | L | IN | 9 | D7 |
Signals
- GND — Signal ground; User Port pin A connects to PC parallel port pin 25.
- PB0–PB2 — CIA #2 Port B bits 0–2; configured as outputs by the C64. They connect to the PC parallel port’s status inputs /ACK (pin 10), BUSY (pin 11), and PE (pin 12) respectively.
- PB3–PB7 — CIA #2 Port B bits 3–7; configured as inputs by the C64. They receive data from the PC parallel port data lines D3–D7 (pins 5–9).
Notes
The C64 User Port connector is a 24-pin DZM 12 DREH card-edge type (3.96 mm pitch, 1.57 mm card thickness). Port B of CIA #2 is individually programmable as input or output per bit via the Data Direction Register B at address $DD03; 64net configures the lower three bits as outputs and the upper five as inputs. The PC end is an SPP (Standard Parallel Port) 25-pin D-sub male. Cable length should be kept short — parallel port signalling is not designed for long runs.