HP 262SA - Communications Line Using a Monitor

Data Communications
In group poll operations the last three characters of the poll sequence(second ,ENQ,P AD) may
be distorted due to the response ofpolled terminals (see figure 7-23). Once a terminal detects
the first double quote character ("), it begins its response with a transition on the Request to
Send (CA) line. This causes the monitor to begin watching for data from the terminal instead of
the computer. This distortion occurs only within the monitor and does not affect the operation
of either the computer or the other terminals.
If the monitor terminal is configured with a communications buffer that is smaller than that
being used by either the computer or responding terminals a data overrun may occur (this
error may, however, also occur at high baud rates regardless of the buffer size). A cancel
character (octal 030) will be displayed at the point where the data overrun occurred (see figure
7-24).
To help prevent data overrun, make sure that the buffer used in the monitor is at least as
large as the largest buffer used by any responding terminal.
Terminal
AA
Terminal
AS
Terminal in
Monitor Mode
Terminal
AC
Figure 7-21. Communications Line Using a Monitor
7-45