SATO ct4i manual Interface Signals, Signal Signal Definition, Receive Buffer Control

Unit 2: Technical Data

ALL INTERFACES

Receive Buffer

The data stream is received from the host to the printer one job at a time. This allows the software program to maintain control of the job print queue so that it can move a high priority job in front of ones of lesser importance. A multiple job buffer allows the printer to continuously receive print jobs while compiling and printing other jobs at the same time. It acts much like a Print buffer to maximize the performance of the host and the printer.

The printer receives and prints one job at a time. If a print job exceeds the buffer size, transmission will be rejected by the printer. Error conditions that occur during the Print Data transmission will cause the printer to return a NAK.

ACK/NAK Protocol

Bi-Directional ACK/NAK protocol is used for error control. In a normal transmission sequence when the transmission is received, the printer will return an ACK (06H) signifying that it was received without a transmission error. After the transmission command structure has been analyzed, a status byte is returned to the host. This status byte informs the host of the validity of the command structure.

If the command structure is error free, the printer proceeds with the print operation. When the print operation is completed, a Printer Status message is returned to the host. If an error was detected during the initial transmission sequence, a NAK (15H) will be returned signalling to the host that the received transmission contained errors and must be resent. If the returned Status byte indicates a command structure error, the error must then be corrected before the print data is resent to the printer.

A valid transmission to the printer must be bounded by an STX/ETX pair, with the STX (02H) signifying the start of the Print Data and ending with an ETX (03H) signifying the end.

Status5 Return

This communication protocol is designed for the purpose of monitoring and controlling print data status in the host and featuring various functions.

	INTERFACE SIGNALS
SIGNAL	SIGNAL DEFINITION
FGN	(Frame Ground)
SxD	(Send Data) - Data from the printer to the host.
RxD	(Receive Data) - Data from the host to the printer.
SGN	(Signal Ground)

Note: Depending on the host used, the CS and RS (maintaining at high) may need to be looped on the host side. Refer to host computer documentation for details.

CABLE REQUIREMENTS

DB9	HOST	DIRECTION	DB9	PRINTER
2	Send Data	To Printer	2	Receive Data
3	Receive Data	To Host	3	Send Data
5	Frame Ground	Bi-Directional	5	Frame Ground

	RECEIVE BUFFER CONTROL
Causes For Receive Buffer Near Full	Occurs when the remaining free space of the buffer drops to 0.95MB of 2.95MB
	capacity or when the remaining free space is available for storing 50 of 500 items in
	the history buffer.
Release Of Receive Buffer Near Full	Can be released when the remaining free space rises to 1.95MB or when the
	remaining free space is available for storing 200 items in the history buffer.

CT4i Series Operator Manual 2-13