Unidirectional Parallel Ports
In early parallel ports the data lines were unidirectional (data out only) so it was not easily possible to feed data in to the computer. However, a workaround was possible by using 4 of the 5 status lines. A circuit could be constructed to split each 8-bit byte into two 4-bit nibbles which were fed in sequentially through the status lines. Each pair of nibbles was then re-combined into an 8-bit byte. This same method (with the splitting and recombining done in software) was also used to transfer data between PCs using a laplink cable.
Read more about this topic: Parallel Port
Famous quotes containing the words parallel and/or ports:
“There isn’t a Parallel of Latitude but thinks it would have been the Equator if it had had its rights.”
—Mark Twain [Samuel Langhorne Clemens] (1835–1910)
“When its errands are noble and adequate, a steamboat bridging the Atlantic between Old and New England, and arriving at its ports with the punctuality of a planet, is a step of man into harmony with nature.”
—Ralph Waldo Emerson (1803–1882)