Keysight Technologies 3458A Guide D'utilisation page 120

3 Configuring for Measurements
Bit 6 (weight = 64) Service Request--service is requested and the GPIB SRQ line
is set true. This bit will be set when any other bit of the status register is set and
has been enabled to assert SRQ by the RQS command. It is possible for bit 6 to be
the only bit set such as when an error set a bit in the error register which, in turn,
set bit 6. Later, the error register was read which removed the error bit but left bit
6 set,
Bit 7 (weight = 128) Data Available--a reading or query response is available in
the output buffer.
Reading the status register
The STB? query command reads the status register and returns the weighted sum
of all set bits. The STB? command does not clear the status register. The following
program uses the STB? command to read the contents of the status register.
10 OUTPUT 722."STB?"
20 ENTER 722; A
30 PRINT A
40 END
For example, assume bit 3 (weight = 8) and bit 7 (weight = 128) are set. The above
program returns the sum of the two weights (136).
The STB? command will never reveal bit 4 (Ready for Instructions) set because the
multimeter is busy processing the STB? command and, therefore, is not ready. If
you intend to monitor the ready bit, you must use the GPIB Serial Poll command
to read the status register. If the SRQ line is true, the Serial Poll command clears
all status register bits.* The SRQ line is also returned to false if bit 6 is cleared. If
the SRQ line is false during Serial Poll, the register's contents are not changed.
The following program shows how to read the status register using the Serial Poll
command.
10 P=SPOLL(722)
20 DISP P
30 END
To clear the status register,
OUTPUT 722; "CSB"
[1] Bits 4, 5, and 6 are not cleared if the condition(s) that set the bit(s) still exist.
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Keysight 3458A User's Guide