HP 7470A Interfacing And Programming Manual page 150

Monitor Mode
After the plotter is in the on-line, programmed-on state, two mutually
exclusive monitor modes may be enabled using the set plotter configura- T
tion instruction, ESC . @. Depending upon which monitor mode is
enabled, either all data (including device control instructions) are re­
transmitted to the terminal CRT or only HP-GLdata are retransmitted
as they are parsed from the plotter's buffer. All plotter output responses
are sent to both the computer and terminal. Refer to The Set Plotter
Configuration Instruction, ESC . @,for complete information.
The plotter monitors for a terminal—generatedBreak signal. Receipt of a
Break signal will cause the same results as described under the on-line,
programmed-on state. Then, new plotter on and set plotter configuration
instructions from the computer are required to resume plotting opera­
tions with monitor mode active. The following diagram shows how the
plotter processes data while in monitor mode.
COMPUTER
TERMINAL
MLEJ
3 PLOTTER
PROCESSORf
SCANS FOR
"BREAK"
OUTPUTS J
PLOTTER
INSTRUCTIONS
Monitor Mode
10-8 RS-232-C/CCITT V.24INTERFACING