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.
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Famous quotes containing the words parallel and/or ports:
“The universe expects every man to do his duty in his parallel of latitude.”
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Are to a wise man ports and happy havens.”
—William Shakespeare (1564–1616)