The link port is a 'pseudo' com port, there is a 'clock' line that all transmissions are synchronized on. This clock by default is driven at 50KHz (20 microsec period), and data is latched on the rising edge. Data is transmitted/received 8 bits at a time starting with the MSB. At the default clock rate it takes 160 microsec to complete a transmission. There is a generic control line that can be used to control the flow of communication. Also it appears there is a Synch In/Out pair that helps the VB to synch the send and receive data to the clock. There is a clock pull with a 20 ms period driven out of the Synch Out line at power up of the VB.

Image 1: Link port pins (looking inside the link port) and (untested) pinout for link cable

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