Keysight Technologies 3458A Guide D'utilisation page 118

3 Configuring for Measurements
Using the Input Buffer
In the multimeter's power-on/PRESET NORM state, the input buffer is disabled.
The means the multimeter must process each GPIB command individually and
wait until the command is executed before releasing the GPIB bus or accepting
another command. In most cases, the controller must wait until the bus is
released before it can continue, which ensures synchronization between the
controller and the instrument. This is most noticeable on commands that take a
long time to execute. For example, if you run the complete self-test from remote
(TEST command), the multimeter does not release the GPIB bus until the self test
is complete, approximately 50 seconds.
With the input buffer enabled, the multimeter temporarily stores commands in the
buffer and immediately releases the GPIB bus. The multimeter then retrieves and
executes the commands in the order received, one by one, from the input buffer.
This allows the controller to perform other operations while the multimeter is
executing commands. The following program enables the input buffer prior to
executing the TEST command.
10 OUTPUT 722;"INBUF ON"
20 OUTPUT 722; "TEST"
30 END
The input buffer holds a maximum of 255 characters. If you send more characters
than the input buffer can hold, the multimeter holds the bus until buffer space
becomes available. When space is available, the remaining characters are
accepted into the input buffer and the bus is released.
When using the input buffer, it may be necessary to know when all buffered
commands have been executed. The multimeter provides this information by
setting bit 4 (ready for instructions) in the status register (discussed next). If the
status register is properly enabled, it drives the GPIB's SRQ (service request) line
true. Your controller will acknowledge this if previously programmed to accept
SRQ as an interrupt.
118 Keysight 3458A User's Guide