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Unit 2: Technical Data
CT4i Series Operator Manual 2-13
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.