A Brief Word About; Notes For An Hp-Ib; Notes For An Hp-Il - HP 7470A Interfacing And Programming Manual

A Brief Word about Plotter Output
There are slight differences in the timing of output when the plotter is
used with the HP-IB, HP-IL, or RS-232-C interfaces. Read the para­
graph below which pertains to your system.
Notes for an HP-IB User
When the 7470 has an HP-IB interface, the terminator for an output
statement, denoted [TERM], is a carriage return followed by a line feed.
The output instructions in this chapter should not be used when the
plotter is in listen—onlymode since the plotter in listen-only mode can­
not output anything. Output instructions will be ignored by the plotter
so the computer will get no response to its read statement, and, typi­
cally, the program will halt.
A plotter with an HP-IB interface will respond only when the computer
sends a read command (the plotter is instructed to talk). Therefore, a
read statement should directly follow any output command. When a
second output command is received before data from the first command
has been read, the new data overwrites the old data and the old data is
lost. Refer to Chapter 9 for more information.
Notes for an RS-232-C User
With an RS-232-Cinterface, the 7470's terminator for an output state­
ment, denoted [TERM], is a carriage return, unless the terminator is
modified by an ESC . M command. As soon as an output command has
been parsed by the plotter, output occurs according to the handshake
protocol established by the ESC . M and ESC . N commands. Use of
turnaround delays, intercharacter delays, and an output initiator
should be specified as necessary to assure that output will not be lost
because the computer is not prepared to receive it. The information nec­
essary to assure this should be contained in the documentation for your
computer. Refer to Chapter 10 of this manual for more information.
Notes for an HP-IL User
When the 7470 has an HP-IL interface, the terminator for an output
statement, denoted [TERM], is a carriage return followed by a line feed.
A plotter with an HP-IL interface will only respond when it is instructed
by the controller to talk. Therefore, a read statement should follow any
output command so that the plotter can send the requested information.
There are no special output timing considerations with HP-IL. This is
because data are sent through the interface bit-serially; only one mes­
sage can travel through the loop at a given time. Refer to Chapter 11
and your computer's documentation for more information.
7-2 OBTAINING INFORMATION FROM THE PLOTTER