Keithley 6487 Reference Manual

Model 6487 Reference Manual IEEE-488 Bus Overview D-11
Common commands
Common commands are commands that are common to all devices on the bus. These com-
mands are designated and defined by the IEEE-488.2 standard.
Generally, these commands are sent as one or more ASCII characters that tell the device to
perform a common operation, such as reset. The IEEE-488 bus treats these commands as
data in that ATN is false when the commands are transmitted.
SCPI commands
SCPI commands are commands that are particular to each device on the bus. These com-
mands are designated by the instrument manufacturer and are based on the instrument
model defined by the Standard Commands for Programmable Instruments (SCPI) Consor-
tium’s SCPI standard.
Generally, these commands are sent as one or more ASCII characters that tell the device to
perform a particular operation, such as setting a range or closing a relay. The IEEE-488
bus treats these commands as data in that ATN is false when the commands are
transmitted.
Command codes
Command codes for the various commands that use the data lines are summarized in
Table D-2. Hexadecimal and the decimal values for the various commands are listed in
Table D-3.
Table D-3
Hexadecimal and decimal command codes
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

Keithley 6487 Specifications

General

Type	Picoammeter/Voltage Source
Current Measurement Range	20 fA to 20 mA
Interfaces	GPIB, RS-232
Voltage Burden	< 200 µV
Input Impedance	>10^14 Ω
Power	100 V / 120 V / 220 V / 240 V
Basic Current Measurement Accuracy	0.4%