Parallel interface protocol for bidirectional communications between computer and printer using status lines for transmitting data during a reverse channel operation

摘要

A protocol provides bidirectional communication capability between a host computer and a printer over a parallel interface, the host computer and the printer having a forward channel therebetween for the transfer of signals from the host computer to the printer. The protocol includes conventions for turning the forward channel around so as to establish a reverse channel to allow transfer of data from the printer to the host computer, conventions for controlling the transfer of data from the printer to the host computer over the reverse channel, and conventions for turning the reverse channel back around so as to re- establish the forward channel.