Fujitsu DL3800 manual Protocol Description, Xon/Xoff

INTERFACE INFORMATION

Serial Protocols

A protocol is a set of instructions that control the way data is transmit- ted between devices such as a computer and printer. The protocol ensures that the computer does not send information to the printer faster than the information can be processed. By telling the computer when the printer can receive data, the protocol prevents the printer’s buffer from overflowing.

This printer offers a choice of four different protocols for connection to a variety of computers: XON/XOFF, DTR, and RC. If you computer documentation does not recommend a particular protocol, try DTR. The following table describes the three protocols.

Protocol	Description
XON/XOFF	When the printer is ready to receive data, it sends the
(DC1/DC3)	XON (DC1) code (hex 11). When fewer than 255 bytes
	of space remain in the buffer (or when the printer is
	taken offline), the printer sends the XOFF (DC3) code
	(hex 13). (When the input buffer is configured for 256
	bytes, the buffer limit is reduced from 255 bytes to 63
	bytes.) The computer must stop transmitting data
	within 255 (63) characters of receiving the XOFF code,
	or information may be lost. If paper runs out, the
	printer sends an NAK code (hex 15).
DTR	DTR is a hardware protocol; that is, the DTR signal on
	interface cable pin 20 is used to control the flow of
	data rather than transmission of a character code.
	When the printer is ready to receive data, pin 20 is
	high. When fewer than 255 (63) bytes of space remain
	in the buffer (or when the printer is taken offline), pin
	20 is low. The computer must stop transmitting data
	within 255 (63) characters of DTR being low, or
	information may be lost.
RC	The RC protocol is the same as the DTR protocol,
	except that the Reverse Channel signal (pin 11) is used
	instead of the Data Terminal Ready signal (pin 20).

D-10 User's Manual