User guide

Printer Communication Interfaces
A.2 The Serial Port
A.2.1 Serial Data Character Format
The serial data character format used by the printer is the format used for
normal asynchronous transmission, that is:
• A start bit (space)
• 7 or 8 data bits (1 = mark, 0 = space)
• A parity bit (selectable)
• One or more stop bits
During setup, the use of the parity bit (on or off) and the number of data bits
(7 or 8) that you assign must agree with the computer to which the printer is
connected.
The stop bits do not need to be modified during setup:
• In the printer-to-computer direction, at least 2 stop bits of idle time are
guaranteed, so the printer can send to a computer that requires either 1,
1.5, or 2 stop bits.
• In the computer-to-printer direction, the printer requires only 1 stop bit of
idle time and can handle data sent to it with 1, 1.5, or 2 stop bits.
A.2.2 Serial Data Synchronization
Serial data synchronization is achieved by the printer continuously monitoring
the number of characters in its input buffer and controlling the data flow when
the number of characters reaches a predefined upper or lower threshold value.
During setup, either the XON/XOFF protocol or DTR handshake protocol can
be selected to perform the data flow control function. The protocol selected
must be the same as that used by the data source.
Note
Only the LA600 MultiPrinter supports the communication protocol
XON/XOFF + DTR.
Input Buffer Size and Threshold Values
The input buffer size is selectable during setup.
The input buffer threshold values are the character counts in the buffer at
which data flow control is triggered. Threshold values are usually as follows:
• Normal Upper Level = 128 (number of characters short of the buffer size)
A–2 Printer Communication Interfaces