The XP1571 parallel cable
You should follow these instructions if your drive has no parallel capabilities yet and you want to connect the cable directly onto the periphery chip in the drive. If possible, you shouldn't use this method because, this way, you won't be able to make use of it with a Commodore machine.
You need the following parts to build this cable:
Step 1. Solder one end of the cable right onto the CIA periphery chip inside the drive.
Step 2. Solder the other end of the cable onto the parallel plug. You should have the following connections:
You can find the description of all parts used on the diagrams at the legend page.
Source: The Joe Forster-STA homepage