Editing Parallel port (section)

===Bi-Tronics===
As the printer market expanded, new types of printing mechanisms appeared. These often supported new features and error conditions that could not be represented on the existing port's relatively few status pins. While the IBM solution could support this, it was not trivial to implement and was not at that time being supported. This led to the Bi-Tronics system, introduced by [[Hewlett-Packard|HP]] on their [[HP LaserJet 4|LaserJet 4Si]] in April 1993.<ref>{{cite web |url=http://www.hp.com/hpinfo/newsroom/feature_stories/2004/printerstimeline.pdf |title=Twenty Years of Innovation: HP LaserJet and Inkjet Printers 1984–2004 |author= HP Corporate Archives |date=2004-05-24 |website=www.hp.com |publisher=HP |archive-url=https://web.archive.org/web/20071202142038/http://www.hp.com/hpinfo/newsroom/feature_stories/2004/printerstimeline.pdf |access-date=2021-11-05 |archive-date=2007-12-02 |quote=}}</ref> This used four existing status pins, ERROR, SELECT, PE and BUSY to represent a [[nibble]], using two transfers to send an 8-bit value. Bi-Tronics mode, now known as nibble mode, was indicated by the host pulling the SELECT line high, and data was transferred when the host toggles the AUTOFEED low.  Other changes in the handshaking protocols improved performance, reaching 400,000 cps to the printer, and about 50,000 cps back to the host.<ref>{{cite web |title= Nibble Mode |url= http://madang.ajou.ac.kr/~ydpark/archive/computer/ppi/fapo/nibble.htm |website= Department of Chemistry, Ajou University |url-status= dead |archive-url= https://web.archive.org/web/20170406082832/http://madang.ajou.ac.kr/~ydpark/archive/computer/ppi/fapo/nibble.htm |archive-date= 2017-04-06 |access-date= 2016-10-11 }}</ref> A major advantage of the Bi-Tronics system is that it can be driven entirely in software in the host, and uses otherwise unmodified hardware - all the pins used for data transfer back to the host were already printer-to-host lines.