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The laplink cable connects five output pins of a parallel port to five input pins on the opposing port, for each direction. Due to the lack of an internal timing in the parallel ports, synchronization is implemented via software handshaking: four of the five pins are used for data transfer and one is used for synchronization. The [[Truth value|logical values]] at these pins are read and written directly by the software via an input or output instruction.
This method does not connect the bidirectional data lines of the two devices, in order to avoid both lines being active at the same time. The status lines
Transmission of a [[byte]] is accomplished by dividing it into two [[nibble]]s of four bits each. Each nibble is transmitted by setting the four data lines according to the four nibble bits and then toggling the acknowledge line. This toggle indicates the receiving host that the nibble is ready to be read. Once the receiving host has read the nibble, it toggles its synchronization line to tell the transmitter that the nibble has been read and that a new one may be sent. Both hosts use a toggle on their acknowledge lines to indicate that the read or write operation has been performed. As a result, each host has to wait for a toggle from the other host before proceeding with a new operation.
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