If the SRQ line is asserted, the controller should then perform a serial poll to determine which device requires
service. The 4300B will return an ASCII zero (0) in response to a serial poll if it did not generate the SRQ. A
non-zero number will be returned if it was responsible for asserting SRQ. A serial poll is performed in HP
Basic using the command:
SPOLL(712)
which would poll the device at address 12.
5-9-4. Output Data Terminator
The "D" command determines the type and quantity of terminators that will be used to signal the end of any
data that the 4300B returns to the controller. This includes measured resistance data as well as the response to
the "configuration status" query. The 4300B interprets this command as follows:
D0
C
R
L
F
(default)
D1
C
R
L
F
with EOI asserted
D2
C
R
L
F
D3
C
R
L
F
with EOI asserted
)
The D1 selection is preferred by IEEE-488.2 systems such as National Instruments
®
.
5-9-5. Test Current Control
The "C" command is used to enable or disable the output of the current source. This command is decoded as
follows:
C0
Turns the test current off
C1
Turns the test current on
5-9-6. Display Hold
The display of the 4300B may be frozen from the GPIB bus using the commands listed below. While in the
"hold" mode the A-to-D converter is still performing measurements, but the results are not sent to the 4300B's
display or to the IEEE output buffer. Therefore once a trigger is sent or tracking is resumed, the display will
instantly reflect the latest measurement. The 4300B interprets these commands as follows:
T
selects continuous tracking mode (default)
S
selects hold mode; also used to trigger a single reading while in the hold mode
