The pin gets connected to the TX and RX pins of the converter. I built one that works OK and I put a 1k resistor connected to the TX pin and a 1N914 diode with the band end connected to the RX pin. Then, tie the other ends of both together and connect to the data pin of the ALDL port. I'm not sure if those components help, but it's the way a pre-made cable is built and I had the parts. The GND in the ALDL port gets connected to the GND of the converter.