Operation
Chapter 3
GPIB-232CV User Manual
3-6
© National Instruments Corp.
be unaddressed to listen and addressed to talk so that data can be sent from
the GPIB device to the GPIB-232CV.
Time Termination Mode
In time termination mode, the GPIB-232CV will address the GPIB device
to talk if the GPIB-232CV serial input buffer becomes empty and no more
serial characters are received for 300 ms. After this period of inactivity, the
GPIB-232CV assumes that since no more serial data is being sent, the
GPIB device might have data that it needs to send back to the
GPIB-232CV. Any characters read from the GPIB port at this time will
immediately be passed along to the serial port. When a serial character is
received by the GPIB-232CV, it immediately re-addresses the GPIB device
to listen and passes the received character to it. It will remain in this mode
until its serial-input buffer becomes empty and no serial characters are
received for 300 ms, at which time it will re-address the GPIB device to
talk.
Time termination mode should be used for applications in which
bidirectional communication is required and neither a <CR> or <LF>
character is used to signal the end of a command string to the GPIB device.
<CR> or <LF> Termination Mode
If a command string to the GPIB instrument can be terminated with either a
<CR> or <LF> character, you can use either <CR> or <LF> termination
mode to address the GPIB device to send data. In these modes, when the
GPIB-232CV receives the terminating character, it will address the GPIB
device to talk so that any GPIB data can be input by the GPIB-232CV. Any
serial character received by the GPIB-232CV at this point will signal the
GPIB-232CV to re-address the GPIB device as a Listener. For example,
let's say you wish to connect an HP7475 GPIB plotter to an IBM-PC serial
port via the GPIB-232CV and you want to draw a line, get plotter status,
and then draw a circle. In BASIC, this could be done with the following
commands:
Содержание GPIB-232CV
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