This chapter discusses parallel communications. The Centronics printer interface transmits 8 bits of data at a time to an external device, normally a printer. Normally it uses a 25-pin D-type connector to connect to a 36-pin Centronics printer interface. In the past, it has been one of the most under used parts of a PC and was not normally used to interface to other equipment. This was because, as a standard, it could only transmit data in one direction (from the PC to the external device). Some interface devices overcame this by using four of the input handshaking lines to input data and then multiplexing using an output handshaking line to multiplex them to produce 8 output bits.
KeywordsData Line Output Line External Device Parallel Port Push Button
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