Typical Command Sequences - Keithley 6430 Instruction Manual

D-12 IEEE-488 Bus Overview

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 D-3 lists a typical bus sequence for send-
ing 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.
Table D-3
Typical addressed multiline command sequence
Step
*Assumes primary address = 24.
Table D-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 D-4
Typical addressed common command sequence
Step
*Assumes primary address = 24.
Command ATN state
1 UNL Set low
2 LAG* Stays low
3 SDC Stays low
4 Returns high
Command ATN state
1 UNL Set low
2 LAG* Stays low
3 Data Set high
4 Data Stays high
5 Data Stays high
6 Data Stays high
Data bus
ASCII Hex
? 3F
8 38
EOT 04
Data bus
ASCII Hex
? 3F
8 38
* 2A
R 52
S 53
T 54
Decimal
63
56
4
Decimal
63
56
42
82
83
84