Fujitsu DL6400 manual Serial Protocols, On/Xoff, Etx/Ack

DL6400/6600 Book Page 12 Friday, July 31, 1998 11:42 AM

Serial Protocols

Serial Protocols	A protocol is a set of instructions that control the way data is
	transmitted between devices such as a processor and printer. The
	protocol ensures that the processor does not send information to the
	printer faster than the data can be processed. By telling the processor
	when it can receive data, the protocol prevents the printer buffer from
	overflowing.
	This printer offers a choice of four protocols: XON/XOFF, DTR, RC,
	and ETX/ACK. The following table gives details. If no particular
	protocol is recommended, try DTR.
	Table C–1 Serial protocols
	Protocol	Description
	ON/XOFF	When the printer is ready to receive data, it sends
	(DC1/DC3)	the XON (DC1) code (hex 11). When fewer than
		255 bytes of space remain in the buffer, or when the
		printer is switched offline, the printer sends the
		XOFF (DC3) code (hex 13). The processor must
		stop transmitting data within 255 (63) characters of
		receiving XOFF, or information may be lost.
	DTR	The DTR signal on interface cable pin 20 controls
	(hardware)	the flow of data rather than sending a character
		code.
	RC	Same as DTR except that it uses the Reverse
		Channel signal (pin 11) instead of the Data
		Terminal Ready signal (pin 20).
	ETX/ACK	This protocol is a little more complicated, but allows
		faster throughput under some conditions. The
		processor adds the End of Text ETX character
		(hex 03) at the end of each block of print data. The
		block, including the ETX character, is usually half
		the printer input buffer, but it can be as large as the
		input buffer.
		The processor must stop transmitting the next block
		of data until it receives the ACK character, or
		information may be lost. Data transmission
		continues until the printer finishes printing two
		blocks, providing high-throughput data
		communication.

C-12 User’s Manual