Keithley 6514, Instruction Manual

Page: 316 / 334

IEEE-488 Bus Overview F-11
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
will respond to addressed commands. Table F-3 lists a typical bus sequence for sending the
addressed multiline commands. In this instance, the SDC command is being sent to the instru-
ment. 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.
Table F-4 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.
Table F-3
Typical bus 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
2E
04 63
46
4
*Assumes primary address = 14.
Table F-4
Typical addressed 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
2E
2A
52
53
54 63
46
42
82
83
84
*Assumes primary address = 14.