Appendix D: IEEE-488 bus overview
Model 6517B Electrometer Reference Manual
D-12
6517B-901-01 Rev. C / August 2015
Typical command sequences
For the various multiline commands, a specific bus sequence must take place to properly send the
command. In particular, the correct listen address must be sent to the instrument before it responds
to addressed commands. The following table lists a typical bus sequence for sending the addressed
multiline commands. In this instance, the
SDC
command is being sent to the instrument.
UNL
is
generally sent as part of the sequence to ensure that no other active listeners are present. Note that
ATN
is true for both the listen command and the
SDC
command byte itself.
Typical addressed command sequence
Step Command ATN
state
Data bus
ASCII Hex Decimal
1
2
3
4
UNL
LAG*
SDC
Set low
Stays low
Stays low
Returns high
?
;
EOT
3F
3B
04
63
59
4
*Assumes primary address = 27
The below table gives a typical common command sequence. In this instance,
ATN
is true while the
instrument is being addressed, but it is set high while sending the common command string.
Typical common command sequence
Step Command ATN
state
Data bus
ASCII Hex Decimal
1
2
3
4
5
6
UNL
LAG*
Data
Data
Data
Data
Set low
Stays low
Set high
Stays high
Stays high
Stays high
?
;
*
R
S
T
3F
3B
2A
52
53
54
63
59
42
82
83
84
*Assumes primary address = 27
IEEE command groups
Command groups supported by the Model 6517B are listed in the following table. Common
commands and SCPI commands are not included in this list.
IEEE command groups
Handshake command group
NDAC
= Not data accepted
NRFD
= Not ready for data
DAV
= Data valid
