Instruction manual

A758 Owner’s Guide Chapter 6: Communiction Interface
September 1999 91
RS-232C Interface
The RS-232C interface uses either the XON/XOFF (software) or DTR/DSR
(hardware) protocol to control the flow of information between the computer and
the printer. For XON/XOFF, a particular character is sent back and forth between
the host and the printer to regulate the communication. For DTR/DSR, changes
in the DTR/DSR signal on the RS 232 interface coordinate the information flow.
The RS-232C interface offers standard settings that are selected with the
Configuration Menu. Use of the Configuration Menu is described in
“Configuring the Printer” in this manual.
Print Speed and Timing
The fast speed of the printer requires the application to send data to the printer at
least as fast as it is printed. The application must also allow output lines to be
buffered ahead at the printer, so the printer will be able to print each line
immediately after the preceding line, without stopping to wait for more data.
Ideally, the application will send all the data for an entire receipt or slip without
pausing between characters or lines transmitted.
If the application sends data at 9600 baud and pauses between lines for as short a
time as 50 milliseconds, the printer will never be able to print at full speed.
However, if the application sends data at 19.2 K baud and does not pause
between lines, the printer will be able to print at its full speed of 2400
lines/minute. The table below shows that with a pause of 50 milliseconds after
each line, the transmit time equals or exceeds the printer process time, slowing
down the printer, regardless of the baud rate.
50ms Pause after Each Line
Characters/Line Lines/Receipt Transmit Time
(19.2 K Baud)
Process Time*
20 20 1.2 Seconds 0.5 Seconds
20 40 2.4 Seconds 1.0 Seconds
44 20 1.44 Seconds 0.5 Seconds
44 40 2.88 Seconds 1.0 Seconds
* Process Time is the time it would take the printer to process the data if all
transmitted data was present. (It is not the time it takes to print the receipt.)
Example: 20 characters/line, with 20 lines = 0.5 seconds process time for the
printer. It takes 1.2 seconds to send the data to the printer at 19.2K-baud speed
with a 50ms delay after each line. Thus the printer would have to wait 0.7
seconds longer to receive the data than it could process it if no delays existed and
the transmission speed were faster.