The port is used in the same ways as the link port on the TI85. PDR is used to send and receive data. The base is always used for ground. The state of the tip and the middle can be set using the following values. White wire is positive.
Red wire is positive.
D4 White wire is positive. Red wire is grounded. E8 White wire is grounded. Red wire is positive. FC Whits wire is grounded.