User manual

IEEE-488 Bus Overview
2001-900-01 Rev. K / August 2010 G-7
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 be-
fore it will respond to addressed commands. Table G-3 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 se-
quence 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 G-4 gives a typical common command sequence. In
this instance, ATN is true while the instrument is being ad-
dressed, but it is set high while sending the common com-
mand string.
Command Hex value
Decimal
value
GTL
SDC
GET
LLO
DCL
SPE
SPD
LAG
TAG
SCG
UNL
UNT
01
04
08
11
14
18
19
20-3F
40-5F
60-7F
3F
5F
1
4
8
17
20
24
25
32-63
64-95
96-127
63
95
q~ÄäÉ=dJO
Hexadecimal and decimal command values
Step Command ATN state
Data bus
ASCII Hex Decimal
1
2
3
4
UNL
LAG*
SDC
Set low
Stays low
Stays low
Returns
high
?
0
EOT
3F
30
04
63
48
4
*Assumes primary address = 16.
q~ÄäÉ= dJP
Typical bus sequence for addressed multiline commands
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
?
0
*
R
S
T
3F
30
2A
52
53
54
63
48
42
82
83
84
Assumes primary address = 16.
q~ÄäÉ=dJQ
Typical common command sequence