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Programming Guide
Agilent Technologies
DC Electronic Loads
Models N3300A, N3301A, N3302A,
N3303A, N3304A, N3305A, and N3306A
Part No. 5964-8198 Printed in U.S.A.
Microfiche No 5964-8199 November, 2000
Safety Summary
The beginning of the electronic load User's Guide has a Safety Summary page. Be sure you are familiar
with the information on this page before programming the electronic load from a controller.
Printing History
The edition and current revision of this manual are indicated below. Reprints of this manual containing
minor corrections and updates may have the same printing date. Revised editions are identified by a new
printing date. A revised edition incorporates all new or corrected material since the previous printing date.
Changes to the manual occurring between revisions are covered by change sheets shipped with the
manual.
This document contains proprietary information protected by copyright. All rights are reserved. No part of
this document may be photocopied, reproduced, or translated into another language without the prior
consent of Agilent Technologies. The information contained in this document is subject to change without
notice.
Copyright 2000 Agilent Technologies Edition 1 _________August, 2000
Update1 _________November, 2000
2
Table of Contents
Safety Summary 2
Printing History 2
Table of Contents 3
1 - GENERAL INFORMATION 9
About this Guide 9
Documentation Summary 9
External References 9
SCPI References 9
GPIB References 10
VXIplug&play Power Products Instrument Drivers 10
Supported Applications 10
System Requirements 10
Downloading and Installing the Driver 10
Accessing Online Help 11
2 - INTRODUCTION TO PROGRAMMING 13
GPIB Capabilities of the Electronic Load 13
GPIB Address 13
RS-232 Capabilities of the Electronic Load 14
RS-232 Data Format 14
RS-232 Flow Control 14
Introduction to SCPI 15
Conventions Used in This Guide 15
Types of SCPI Commands 15
Multiple Commands in a Message 16
Moving Among Subsystems 16
Including Common Commands 16
Using Queries 17
Types of SCPI Messages 17
The Message Unit 17
Headers 17
Query Indicator 18
Message Unit Separator 18
Root Specifier 18
Message Terminator 18
SCPI Data Formats 18
Numerical Data Formats 18
Suffixes and Multipliers 19
Response Data Types 19
SCPI Command Completion 19
Using Device Clear 20
RS-232 Troubleshooting 20
SCPI Conformance Information 21
SCPI Conformed Commands 21
Non-SCPI Commands 21
3
3 - PROGRAMMING EXAMPLES 23
Introduction 23
Programming the Input 23
Power-on Initialization 23
Enabling the Input 23
Input Voltage 23
Input Current 24
Setting the Triggered Voltage or Current Levels 24
Programming Transients 25
Continuous Transients 25
Pulse Transients 25
Toggled Transients 26
Programming Lists 26
Programming Lists for Multiple Channels 28
Triggering Transients and Lists 29
SCPI Triggering Nomenclature 29
List Trigger Model 29
Initiating List Triggers 30
Specifying a Trigger Delay 30
Generating Transient and List Triggers 30
Making Measurements 31
Voltage and Current Measurements 31
Triggering Measurements 33
SCPI Triggering Nomenclature 33
Measurement Trigger Model 33
Initiating the Measurement Trigger System 34
Generating Measurement Triggers 34
Controlling Measurement Samples 35
Varying the Sampling Rate 35
Measurement Delay 35
Multiple Measurements 35
Synchronizing Transients and Measurements 36
Measuring Triggered Transients or Lists 36
Measuring Dwell-Paced Lists 37
Programming the Status Registers 38
Power-On Conditions 41
Channel Status Group 41
Channel Summary Group 41
Questionable Status Group 41
Standard Event Status Group 41
Operation Status Group 42
Status Byte Register 42
Determining the Cause of a Service Interrupt 43
Servicing Standard Event Status and Questionable Status Events 43
Programming Examples 44
CC Mode Example 44
CV Mode Example 44
CR Mode Example 45
Continuous Transient Operation Example 45
Pulsed Transient Operation Example 46
Synchronous Toggled Transient Operation Example 46
Battery Testing Example 47
Power Supply Testing Example 49
C++ Programming Example 50
4
4 - LANGUAGE DICTIONARY 53
Introduction 53
Subsystem Commands 53
Common Commands 54
Programming Parameters 54
Calibration Commands 55
CALibrate:DATA 55
CALibrate:IMON:LEVel 55
CALibrate:IPR:LEVel 55
CALibrate:LEVel 55
CALibrate:PASSword 56
CALibrate:SAVE 56
CALibrate:STATe 56
Channel Commands 57
CHANnel INSTrument 57
Input Commands 58
[SOURce:]INPut OUTPut 58
[SOURce:]INPut:PROTection:CLEar OUTput:PROTection:CLEar 58
[SOURce:]INPut:SHORt OUTPut:SHORt 58
[SOURce:]CURRent 59
[SOURce:]CURRent:MODE 59
[SOURce:]CURRent:PROTection 59
[SOURce:]CURRent:PROTection:DELay 60
[SOURce:]CURRent:PROTection:STATe 60
[SOURce:]CURRent:RANGe 60
[SOURce:]CURRent:SLEW 61
[SOURce:]CURRent:SLEW:NEGative 61
[SOURce:]CURRent:SLEW:POSitive 61
[SOURce:]CURRent:TLEVel 62
[SOURce:]CURRent:TRIGgered 62
[SOURce:]FUNCtion [SOURce:]MODE 62
[SOURce:]FUNCtion:MODE 63
[SOURce:]RESistance 63
[SOURce:]RESistance:MODE 63
[SOURce:]RESistance:RANGe 64
[SOURce:]RESistance:SLEW 64
[SOURce:]RESistance:SLEW:NEGative 64
[SOURce:]RESistance:SLEW:POSitive 65
[SOURce:]RESistance:TLEVel 65
[SOURce:]RESistance:TRIGgered 65
[SOURce:]VOLTage 66
[SOURce:]VOLTage:MODE 66
[SOURce:]VOLTage:RANGe 66
[SOURce:]VOLTage:SLEW 67
[SOURce:]VOLTage:SLEW:NEGative 67
[SOURce:]VOLTage:SLEW:POSitive 68
[SOURce:]VOLTage:TLEVel 68
[SOURce:]VOLTage:TRIGgered 68
Measurement Commands 69
ABORt 69
MEASure:ARRay:CURRent? FETCh:ARRay:CURRent? 69
MEASure:ARRay:POWer? FETCh:ARRay:POWer? 69
MEASure:ARRay:VOLTage? FETCh:ARRay:VOLTage? 70
5
MEASure:CURRent? FETCh:CURRent? 70
MEASure:CURRent:ACDC? FETCh:CURRent:ACDC? 70
MEASure:CURRent:MAXimum? FETCh:CURRent:MAXimum? 70
MEASure:CURRent:MINimum? FETCh:CURRent:MINimum? 71
MEASure:POWer? FETCh:POWer? 71
MEASure:POWer:MAXimum? FETCh:POWer:MAXimum? 71
MEASure:POWer:MINimum? FETCh:POWer:MINimum? 71
MEASure:VOLTage? FETCh:VOLTage? 72
MEASure:VOLTage:ACDC? FETCh:VOLTage:ACDC? 72
MEASure:VOLTage:MAXimum? FETCh:VOLTage:MAXimum? 72
MEASure:VOLTage:MINimum? FETCh:VOLTage:MINimum? 72
SENSe:CURRent:RANGe 73
SENSe:SWEep:POINts 73
SENSe:SWEep:OFFSet 73
SENSe:SWEep:TINTerval 74
SENSe:WINDow 74
SENSe:VOLTage:RANGe 74
Port Commands 75
PORT0 75
PORT1 75
List Commands 76
[SOURce:]LIST:COUNt 76
[SOURce:]LIST:CURRent [SOURce:]LIST:CURRent:POINts? 76
[SOURce:]LIST:CURRent:RANGe [SOURce:]LIST:CURRent:RANGe:POINts? 77
[SOURce:]LIST:CURRent:SLEW [SOURce:]LIST:CURRent:SLEW:POINts? 77
[SOURce:]LIST:CURRent:SLEW:NEGative 78
[SOURce:]LIST:CURRent:SLEW:POSitive 78
[SOURce:]LIST:CURRent:TLEVel [SOURce:]LIST:CURRent:TLEVel:POINts? 78
[SOURce:]LIST:FUNCtion [SOURce:]LIST:MODE [SOURce:]LIST:FUNCtion:POINTs? 79
[SOURce:]LIST:DWELl [SOURce:]LIST:DWELl:POINts? 79
[SOURce:]LIST:RESistance [SOURce:]LIST:RESistance:POINts? 80
[SOURce:]LIST:RESistance:RANGe [SOURce:]LIST:RESistance:RANGe:POINts? 80
[SOURce:]LIST:RESistance:SLEW [SOURce:]LIST:RESistance:SLEW:POINts? 81
[SOURce:]LIST:RESistance:SLEW:NEGative 81
[SOURce:]LIST:RESistance:SLEW:POSitive 81
[SOURce:]LIST:RESistance:TLEVel [SOURce:]LIST:RESistance:TLEVel:POINTs? 82
[SOURce:]LIST:STEP 82
[SOURce:]LIST:TRANsient [SOURce:]LIST:TRANsient:POINts? 82
[SOURce:]LIST:TRANsient:DCYCle [SOURce:]LIST:TRANsient:DCYCle:POINts? 83
[SOURce:]LIST:TRANsient:FREQuency [SOURce:]LIST:TRANsient:FREQuency:POINts? 83
[SOURce:]LIST:TRANsient:MODE [SOURce:]LIST:TRANsient:MODE:POINts? 83
[SOURce:]LIST:TRANsient:TWIDth [SOURce:]LIST:TRANsient:TWIDth:POINts? 84
[SOURce:]LIST:VOLTage [SOURce:]LIST:VOLTage:POINts? 84
[SOURce:]LIST:VOLTage:RANGe [SOURce:]LIST:VOLTage:RANGe:POINTs? 84
[SOURce:]LIST:VOLTage:SLEW [SOURce:]LIST:VOLTage:SLEW:POINts? 85
[SOURce:]LIST:VOLTage:SLEW:NEGative 85
[SOURce:]LIST:VOLTage:SLEW:POSitive 86
[SOURce:]LIST:VOLTage:TLEVel [SOURce:]LIST:VOLTage:TLEVel:POINts? 86
Transient Commands 87
[SOURce:]TRANsient 87
[SOURce:]TRANsient:DCYCle 87
[SOURce:]TRANsient:FREQuency 87
[SOURce:]TRANsient:MODE 88
[SOURce:]TRANsient:LMODE 88
[SOURce:]TRANsient:TWIDth 88
6
Status Commands 89
Bit Configuration of Channel Status Registers 89
STATus:CHANnel? 89
STATus:CHANnel:CONDition? 89
STATus:CHANnel:ENABle 89
STATus:CSUM? 90
STATus:CSUMmary:ENABle 90
Bit Configuration of Operation Status Registers 90
STATus:OPERation? 90
STATus:OPERation:CONDition? 90
STATus:OPERation:ENABle 91
STATus:OPERation:NTRansition STATus:OPERation:PTRansition 91
Bit Configuration of Questionable Status Registers 92
STATus:QUEStionable? 92
STATus:QUEStionable:CONDition? 92
STATus:QUEStionable:ENABle 92
System Commands 93
SYSTem:ERRor? 93
SYSTem:LOCal 93
SYSTem:REMote 93
SYSTem:RWLock 93
SYSTem:VERSion? 93
Trigger Commands 94
ABORt 94
INITiate:SEQuence INITiate:NAME 94
INITiate:SEQuence2 INITiate:NAME 94
INITiate:CONTinuous:SEQuence INITiate:CONTinuous:NAME 95
TRIGger 95
TRIGger:DELay 95
TRIGger:SEQuence2:COUNt 96
TRIGger:SOURce 96
TRIGger:TIMer 96
Common Commands 97
*CLS 97
*ESE 97
Bit Configuration of Standard Event Status Enable Register 98
*ESR? 98
*IDN? 98
*OPC 98
*OPT? 99
*PSC 99
*RCL 99
*RDT? 100
*RST 100
*SAV 101
*SRE 101
*STB? 101
Bit Configuration of Status Byte Register 102
*TRG 102
*TST? 102
*WAI 102
7
A - SCPI COMMAND TREE 103
Command Syntax 103
B - ERROR MESSAGES 107
Error Number List 107
C - COMPARING N3300A ELECTRONIC LOADS WITH EARLIER MODELS 111
Introduction 111
INDEX 115
8
1
General Information
About this Guide
This manual contains programming information for the Agilent Technologies N3301A, N3302A, N3303A,
N3304A, N3305A, N3306A Electronic Load modules when installed in an Agilent Technologies N3300A
and N3301A Electronic Load mainframes. These units will be referred to as "electronic load" throughout
this manual. You will find the following information in the rest of this guide:
Chapter 1 Introduction to this guide.
Chapter 2 Introduction to SCPI messages structure, syntax, and data formats.
Chapter 3 Introduction to programming the electronic load with SCPI commands.
Chapter 4 Dictionary of SCPI commands.
Appendix A SCPI command tree.
Appendix B Error messages
Appendix C Comparison With Earlier Models
Documentation Summary
The following documents that are related to this Programming Guide have additional helpful information
for using the electronic load.
K Quick Start Guide - located in the front part of the User's Guide. Information on how to quickly get
started using the electronic load.
K User's Guide. Includes specifications and supplemental characteristics, how to use the front
panel, how to connect to the instrument, and calibration procedures.
External References
SCPI References
The following documents will assist you with programming in SCPI:
K Beginner's Guide to SCPI. Part No. H2325-90001. Highly recommended for anyone who has not
had previous experience programming with SCPI.
K Tutorial Description of the GPIB . Part No. 5952-0156. Highly recommended for those not familiar
with the IEEE 488.1 and 488.2 standards.
To obtain a copy of the above documents, contact your local Agilent Technologies Sales and Support
Office.
9
1 - General Information
GPIB References
The most important GPIB documents are your controller programming manuals - GW BASIC, GPIB
Command Library for MS DOS, etc. Refer to these for all non-SCPI commands (for example: Local
Lockout).
The following are two formal documents concerning the GPIB interface:
K ANSI/IEEE Std. 488.1-1987 IEEE Standard Digital Interface for Programmable Instrumentation.
Defines the technical details of the GPIB interface. While much of the information is beyond the
need of most programmers, it can serve to clarify terms used in this guide and in related
documents.
K ANSI/IEEE Std. 488.2-1987 IEEE Standard Codes, Formats, Protocols, and Common
Commands. Recommended as a reference only if you intend to do fairly sophisticated
programming. Helpful for finding precise definitions of certain types of SCPI message formats,
data types, or common commands.
The above two documents are available from the IEEE (Institute of Electrical and Electronics Engineers),
345 East 47th Street, New York, NY 10017, USA.
VXIplug&play Power Products Instrument Drivers
VXIplug&play instrument drivers for Microsoft Windows 95 and Windows NT are now available on the
Web at http://www.agilent.com/find/drivers. These instrument drivers provide a high-level programming
interface to your Agilent Technologies electronic load. VXIplug&play instrument drivers are an alternative
to programming your instrument with SCPI command strings. Because the instrument driver's function
calls work together on top of the VISA I/O library, a single instrument driver can be used with multiple
application environments.
Supported Applications
a Agilent VEE
a Microsoft Visual BASIC
a Microsoft Visual C/C++
a Borland C/C++
a National Instruments LabVIEW
a National Instruments LabWindows/CVI
System Requirements
The VXIplug&play instrument driver complies with the following:
a Microsoft Windows 95
a Microsoft Windows NT 4.0
a HP VISA revision F.01.02
a National Instruments VISA 1.1
Downloading and Installing the Driver
NOTE: Before installing the VXIplug&play instrument driver, make sure that you have one of the
supported applications installed and running on your computer.
10
General Information - 1
1. Access Agilent Technologies Web site at http://www.agilent.com/find/drivers.
2. Select the instrument for which you need the driver.
3. Click on the driver, either Windows 95 or Windows NT, and download the executable file to your
PC.
4. Locate the file that you downloaded from the Web. From the Start menu select Run
:\agxxxx.exe - where is the directory path where the file is located, and agxxxx is
the instrument driver that you downloaded .
5. Follow the directions on the screen to install the software. The default installation selections will
work in most cases. The readme.txt file contains product updates or corrections that are not
documented in the on-line help. If you decide to install this file, use any text editor to open and
read it.
6. To use the VXIplug&play instrument driver, follow the directions in the VXIplug&play online help
for your specific driver under "Introduction to Programming".
Accessing Online Help
A comprehensive online programming reference is provided with the driver. It describes how to get
started using the instrument driver with Agilent VEE, LabVIEW, and LabWindows. It includes complete
descriptions of all function calls as well as example programs in C/C++ and Visual BASIC.
a To access the online help when you have chosen the default Vxipnp start folder, click on the Start
button and select Programs | Vxipnp | Agxxxx Help (32-bit).
- where Agxxxx is the instrument driver.
11
2
Introduction to Programming
GPIB Capabilities of the Electronic Load
All electronic load functions except for setting the GPIB address are programmable over the GPIB. The
IEEE 488.2 capabilities of the electronic load are described in Table 2-1. Refer to Appendix A of your
User's Guide for its exact capabilities.
Table 2-1. IEEE 488 Capabilities of Electronic Loads
GPIB Capabilities Response Interface
Function
Talker/Listener All electronic load functions except for setting the GPIB address are AH1, SH1,
programmable over the GPIB. The electronic load can send and T6. L4
receive messages over the GPIB. Status information is sent using a
serial poll. Front panel annunciators indicate the present GPIB state
of the electronic load.
Service Request The electronic load sets the SRQ line true if there is an enabled SR1
service request condition. Refer to Chapter 3 - Status Reporting for
more information.
Remote/Local In local mode, the electronic load is controlled from the front panel RL1
but will also execute commands sent over the GPIB. The electronic
load powers up in local mode and remains in local mode until it
receives a command over the GPIB. Once the electronic load is in
remote mode the front panel RMT annunciator is on, all front panel
keys (except ) are disabled, and the display is in normal
metering mode. Pressing on the front panel returns the
electronic load to local mode. can be disabled using local
lockout so that only the controller or the power switch can return the
electronic load to local mode.
Device Trigger The electronic load will respond to the device trigger function. DT1
Group Execute The electronic load will respond to the group execute trigger function. GET
Trigger
Device Clear The electronic load responds to the Device Clear (DCL) and DCL, SDC
Selected Device Clear (SDC) interface commands. They cause the
electronic load to clear any activity that would prevent it from
receiving and executing a new command (including *WAI and
*OPC?). DCL and SDC do not change any programmed settings.
GPIB Address
The electronic load operates from a GPIB address that is set from the front panel. To set the GPIB
address, press the Address key on the front panel and enter the address using the Entry keys. The
address can be set from 0 to 30. The GPIB address is stored in non-volatile memory.
13
2 - Introduction to Programming
RS-232 Capabilities of the Electronic Load
The electronic load provides an RS-232 programming interface, which is activated by commands located
under the front panel Address key. All SCPI commands are available through RS-232 programming.
When the RS-232 interface is selected, the GPIB interface is disabled.
The EIA RS-232 Standard defines the interconnections between Data Terminal Equipment (DTE) and
Data Communications Equipment (DCE). The electronic load is designed to be a DTE. It can be
connected to another DTE such as a PC COM port through a null modem cable.
NOTE: The RS-232 settings in your program must match the settings specified in the front panel
Address menu. Press the front panel Address key if you need to change the settings.
RS-232 Data Format
The RS-232 data is a 10-bit word with one start bit and one stop bit. The number of start and stop bits is
not programmable. However, the following parity options are selectable using the front panel Address key:
EVEN Seven data bits with even parity
ODD Seven data bits with odd parity
MARK Seven data bits with mark parity (parity is always true)
SPACE Seven data bits with space parity (parity is always false)
NONE Eight data bits without parity
Parity options are stored in non-volatile memory.
Baud Rate
The front panel Address key lets you select one of the following baud rates, which is stored in non-volatile
memory:
300 600 1200 2400 4800 9600
RS-232 Flow Control
The RS-232 interface supports the following flow control options that are selected using the front panel
Address key. For each case, the electronic load will send a maximum of five characters after holdoff is
asserted by the controller. The electronic load is capable of receiving as many as fifteen additional
characters after it asserts holdoff.
RTS-CTS The electronic load asserts its Request to Send (RTS) line to signal hold-off
when its input buffer is almost full, and it interprets its Clear to Send (CTS)
line as a hold-off signal from the controller.
NONE There is no flow control.
Flow control options are stored in non-volatile memory.
14
Introduction to Programming - 2
Introduction to SCPI
SCPI (Standard Commands for Programmable Instruments) is a programming language for controlling
instrument functions over the GPIB and RS-232 interface. SCPI is layered on top of the hardware-portion
of IEEE 488.2. The same SCPI commands and parameters control the same functions in different classes
of instruments.
Conventions Used in This Guide
Angle brackets < > Items within angle brackets are parameter abbreviations. For example,
indicates a specific form of numerical data.
Vertical bar | Vertical bars separate alternative parameters. For example, NORM | TEXT
indicates that either "TEXT" or "NORM" can be used as a parameter.
Square Brackets [ ] Items within square brackets are optional. The representation [SOURce:].
VOLTage means that SOURce: may be omitted.
Braces { } Braces indicate parameters that may be repeated zero or more times. It is
used especially for showing arrays. The notation {<,B>} shows that
parameter "A" must be entered, while parameter "B" may be omitted or
may be entered one or more times.
Computer font Computer font is used to show program lines in text.
OUTPUT 723 "TRIGger:COUNt:CURRent 10" shows a program line.
Types of SCPI Commands
SCPI has two types of commands, common and subsystem.
Common commands generally are not related to specific operation but to controlling overall
electronic load functions, such as reset, status, and synchronization. All common commands
consist of a three-letter mnemonic preceded by an asterisk: *RST *IDN? *SRE 8
Subsystem commands perform specific electronic load functions. They are organized into an
inverted tree structure with the "root" at the top. The following figure shows a portion of a
subsystem command tree, from which you access the commands located along the various
paths. You can see the complete tree in Appendix A.
ROOT
:CURRent [:LEVel] [:IMMediate]
:MODE
:PROTection [:LEVel]
:DELay
:STATus :OPERation [:EVENt]?
:CONDition?
Figure 2-1. Partial Command Tree
15
2 - Introduction to Programming
Multiple Commands in a Message
Multiple SCPI commands can be combined and sent as a single message with one message terminator.
There are two important considerations when sending several commands within a single message:
Use a semicolon to separate commands within a message.
There is an implied header path that affects how commands are interpreted by the electronic load.
The header path can be thought of as a string that gets inserted before each command within a message.
For the first command in a message, the header path is a null string. For each subsequent command the
header path is defined as the characters that make up the headers of the previous command in the
message up to and including the last colon separator. An example of a message with two commands is:
CURR:LEV 3;PROT:STAT OFF
which shows the use of the semicolon separating the two commands, and also illustrates the header path
concept. Note that with the second command, the leading header "CURR" was omitted because after the
"CURR:LEV 3" command, the header path became defined as "CURR" and thus the instrument
interpreted the second command as:
CURR:PROT:STAT OFF
In fact, it would have been syntactically incorrect to include the "CURR" explicitly in the second command,
since the result after combining it with the header path would be:
CURR:CURR:PROT:STAT OFF
which is incorrect.
Moving Among Subsystems
In order to combine commands from different subsystems, you need to be able to reset the header path to
a null string within a message. You do this by beginning the command with a colon (:), which discards any
previous header path. For example, you could clear the output protection and check the status of the
Operation Condition register in one message by using a root specifier as follows:
OUTPut:PROTection:CLEAr;:STATus:OPERation:CONDition?
The following message shows how to combine commands from different subsystems as well as within the
same subsystem:
VOLTage:LEVel 20;PROTection 28; :CURRent:LEVel 3;PROTection:STATe ON
Note the use of the optional header LEVel to maintain the correct path within the voltage and current
subsystems, and the use of the root specifier to move between subsystems.
Including Common Commands
You can combine common commands with subsystem commands in the same message. Treat the
common command as a message unit by separating it with a semicolon (the message unit separator).
Common commands do not affect the header path; you may insert them anywhere in the message.
VOLTage:TRIGgered 17.5;:INITialize;*TRG
OUTPut OFF;*RCL 2;OUTPut ON
16
Introduction to Programming - 2
Using Queries
Observe the following precautions with queries:
Set up the proper number of variables for the returned data. For example, if you are reading back
a measurement array, you must dimension the array according to the number of measurements
that you have placed in the measurement buffer.
Read back all the results of a query before sending another command to the electronic load.
Otherwise a Query Interrupted error will occur and the unreturned data will be lost.
Types of SCPI Messages
There are two types of SCPI messages, program and response.
A program message consists of one or more properly formatted SCPI commands sent from the
controller to the electronic load. The message, which may be sent at any time, requests the
electronic load to perform some action.
A response message consists of data in a specific SCPI format sent from the electronic load to
the controller. The electronic load sends the message only when commanded by a program
message called a "query."
The following figure illustrates SCPI message structure:
Data Message Unit
Headers Query Indicator
VOLT:LEV 20 ; TLEV 30 ; : CURR?
Header Separator Message Terminator
Message Unit Separators Root Specifier
Figure 2-2. Command Message Structure
The Message Unit
The simplest SCPI command is a single message unit consisting of a command header (or keyword)
followed by a message terminator. The message unit may include a parameter after the header. The
parameter can be numeric or a string.
ABORt
VOLTage 20
Headers
Headers, also referred to as keywords, are instructions recognized by the electronic load. Headers may be
either in the long form or the short form. In the long form, the header is completely spelled out, such as
VOLTAGE, STATUS, and DELAY. In the short form, the header has only the first three or four letters,
such as VOLT, STAT, and DEL.
17
2 - Introduction to Programming
Query Indicator
Following a header with a question mark turns it into a query (VOLTage?, VOLTage:PROTection?). If a
query contains a parameter, place the query indicator at the end of the last header
(VOLTage:PROTection? MAX).
Message Unit Separator
When two or more message units are combined into a compound message, separate the units with a
semicolon (STATus:OPERation?;QUEStionable?).
Root Specifier
When it precedes the first header of a message unit, the colon becomes the root specifier. It tells the
command parser that this is the root or the top node of the command tree.
Message Terminator
A terminator informs SCPI that it has reached the end of a message. Three permitted messages
terminators are:
newline (), which is ASCII decimal 10 or hex 0A.
end or identify ()
both of the above ().
In the examples of this guide, there is an assumed message terminator at the end of each message.
NOTE: All RS-232 response data sent by the electronic load is terminated by the ASCII character
pair . This differs from GPIB response data which is
terminated by the single character with EOI asserted.
SCPI Data Formats
All data programmed to or returned from the electronic load is ASCII. The data may be numerical or
character string.
Numerical Data Formats
Symbol Data Form
Talking Formats
Digits with an implied decimal point assumed at the right of the least-significant digit.
Examples: 273
Digits with an explicit decimal point. Example: .0273
Digits with an explicit decimal point and an exponent. Example: 2.73E+2
Listening Formats
Extended format that includes , and . Examples: 273 273. 2.73E2
Expanded decimal format that includes and MIN MAX. Examples: 273 273.
2.73E2 MAX. MIN and MAX are the minimum and maximum limit values that are
implicit in the range specification for the parameter.
Boolean Data. Example: 0 | 1 or ON | OFF
18
Introduction to Programming - 2
Suffixes and Multipliers
Class Suffix Unit Unit with Multiplier
Amplitude V volt MV (millivolt)
Current A ampere MA (milliampere)
Power W watt MW (milliwatt)
Resistance OHM ohm MOHM (megohm)
Slew Rate A/s amps/second
R/s ohms/second
V/s volts/second
Time s second MS (millisecond)
Common Multipliers
1E3 K kilo
1E-3 M milli
1E-6 U micro
Response Data Types
Character strings returned by query statements may take either of the following forms, depending on the
length of the returned string:
Character Response Data. Permits the return of character strings.
Arbitrary ASCII Response Data. Permits the return of undelimited 7-bit ASCII. This data type
has an implied message terminator.
String Response Data. Returns string parameters enclosed in double quotes.
SCPI Command Completion
SCPI commands sent to the electronic load are processed either sequentially or in parallel. Sequential
commands finish execution before a subsequent command begins. Parallel commands allow other
commands to begin executing while the parallel command is still executing. Commands that affect trigger
actions are among the parallel commands.
The *WAI, *OPC, and *OPC? common commands provide different ways of indicating when all
transmitted commands, including any parallel ones, have completed their operations. The syntax and
parameters for these commands are described in chapter 4. Some practical considerations for using
these commands are as follows:
*WAI This prevents the electronic load from processing subsequent commands until all
pending operations are completed.
*OPC? This places a 1 in the Output Queue when all pending operations have completed.
Because it requires your program to read the returned value before executing the next
program statement, *OPC? can be used to cause the controller to wait for commands
to complete before proceeding with its program.
*OPC This sets the OPC status bit when all pending operations have completed. Since your
program can read this status bit on an interrupt basis, *OPC allows subsequent
commands to be executed.
NOTE: The trigger system must be in the Idle state in order for the status OPC bit to be true.
Therefore, as far as triggers are concerned, OPC is false whenever the trigger system is
in the Initiated state.
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2 - Introduction to Programming
Using Device Clear
You can send a device clear at any time to abort a SCPI command that may be hanging up the GPIB
interface. The status registers, the error queue, and all configuration states are left unchanged when a
device clear message is received. Device clear performs the following actions:
The input and output buffers of the electronic load are cleared.
The electronic load is prepared to accept a new command string.
The following statement shows how to send a device clear over the GPIB interface using GW BASIC:
CLEAR 705 IEEE-488 Device Clear
The following statement shows how to send a device clear over the GPIB interface using the GPIB
command library for C or QuickBASIC:
IOCLEAR (705)
NOTE: For RS-232 operation, sending a Break will perform the same operation as the IEEE-488
device clear message.
RS-232 Troubleshooting
If you are having trouble communicating over the RS-232 interface, check the following:
The computer and the electronic load must be configured for the same baud rate, parity, number
of data bits, and flow control options. Note that the electronic load is configured for 1 start bit and
1 stop bit (these values are fixed).
The correct interface cables or adapters must be used, as described under RS-232 Connector.
Note that even if the cable has the proper connectors for your system, the internal wiring may be
incorrect.
The interface cable must be connected to the correct serial port on your computer (COM1, COM2,
etc.).
20
Introduction to Programming - 2
SCPI Conformance Information
SCPI Conformed Commands
The Electronic Load conforms to SCPI Version 1995.0.
ABOR MEAS | FETC[:SCAL]:VOLT:MAX [SOUR]:RES[:LEV][:IMM][:AMP]
CAL:DATA MEAS | FETC[:SCAL]:VOLT:MIN [SOUR]:RES[:LEV]:TRIG[:AMP]
CAL:STAT SENS:CURR[:DC]:RANG[:UPP] [SOUR]:RES:MODE
INIT[:IMM]:SEQ SENS:SWE:OFFS [SOUR]:RES:RANG
INIT[:IMM]:NAME SENS:SWE:POIN [SOUR]:RES:SLEW
INIT:CONT:SEQ SENS:SWE:TINT [SOUR]:VOLT[:LEV][:IMM][:AMP]
INIT:CONT:NAME SENS:WIND[:TYPE] [SOUR]:VOLT[:LEV]:TRIG[:AMP]
INP | OUTP[:STAT] SENS:VOLT[:DC]:RANG[:UPP] [SOUR]:VOLT:MODE
INP | OUTP:PROT:CLE [SOUR]:CURR[:LEV][:IMM][:AMP] [SOUR]:VOLT:RANG
MEAS | FETC:ARR:CURR[:DC] [SOUR]:CURR[:LEV]:TRIG[:AMP] [SOUR]:VOLT:SLEW
MEAS | FETC:ARR:POW[:DC] [SOUR]:CURR:MODE STAT:OPER[:EVEN]
MEAS | FETC:ARR:VOLT[:DC] [SOUR]:CURR:PROT[:LEV] STAT:OPER:COND
MEAS | FETC[:SCAL]:CURR[:DC] [SOUR]:CURR:PROT:STAT STAT:OPER:ENAB
MEAS | FETC[:SCAL]:CURR:MAX [SOUR]:CURR:RANG STAT:OPER:NTR
MEAS | FETC[:SCAL]:CURR:MIN [SOUR]:CURR:SLEW STAT:OPER:PTR
MEAS | FETC[:SCAL]:POW[:DC] [SOUR]:LIST:COUN STAT:QUES[:EVEN]
MEAS | FETC[:SCAL]:POW:MAX [SOUR]:LIST:CURR STAT:QUES:COND
MEAS | FETC[:SCAL]:POW:MIN [SOUR]:LIST:DWEL STAT:QUES:ENAB
MEAS | FETC[:SCAL]:VOLT[:DC] [SOUR]:LIST:RES SYST:ERR
[SOUR]:LIST:VOLT SYST:VER
Non-SCPI Commands
CAL:IMON:LEV [SOUR]:LIST:CURR:TLEV [SOUR]:TRAN[:STAT]
CAL:IPR:LEV [SOUR]:LIST:FUNC | MODE [SOUR]:TRAN:DCYC
CAL:LEV [SOUR]:LIST:RES:RANG [SOUR]:TRAN:FREQ
CAL:PASS [SOUR]:LIST:RES:SLEW[:BOTH] [SOUR]:TRAN:MODE
CAL:SAVE [SOUR]:LIST:RES:SLEW:NEG [SOUR]:TRAN:LMOD
CHAN | INST[:LOAD] [SOUR]:LIST:RES:SLEW:POS [SOUR]:TRAN:TWID
INP | OUTP:SHOR[:STAT] [SOUR]:LIST:RES:TLEV [SOUR]:VOLT:SLEW:NEG
MEAS | FETC[:SCAL]:CURR:ACDC [SOUR]:LIST:STEP [SOUR]:VOLT:SLEW:POS
MEAS | FETC[:SCAL]:VOLT:ACDC [SOUR]:LIST:TRAN[:STAT] [SOUR]:VOLT:TLEV
PORT0[:STAT] [SOUR]:LIST:TRAN:DCYC STAT:CHAN[:EVEN]
PORT1[:LEV] [SOUR]:LIST:TRAN:FREQ STAT:CHAN:COND
[SOUR]:CURR:PROT:DEL [SOUR]:LIST:TRAN:MODE STAT:CHAN:ENAB
[SOUR]:CURR:SLEW:NEG [SOUR]:LIST:TRAN:TWID STAT:CSUM[:EVEN]
[SOUR]:CURR:SLEW:POS [SOUR]:LIST:VOLT:RANG STAT:CSUM:ENAB
[SOUR]:CURR:TLEV [SOUR]:LIST:VOLT:SLEW[:BOTH] SYST:LOC
[SOUR]:FUNC | MODE [SOUR]:LIST:VOLT:SLEW:NEG SYST:REM
[SOUR]:FUNC | MODE:MODE [SOUR]:LIST:VOLT:SLEW:POS SYST:RWL
[SOUR]:LIST:CURR:RANG [SOUR]:LIST:VOLT:TLEV TRIG[:IMM]
[SOUR]:LIST:CURR:SLEW[:BOTH] [SOUR]:RES:SLEW:NEG TRIG:DEL
[SOUR]:LIST:CURR:SLEW:NEG [SOUR]:RES:SLEW:POS TRIG:SOUR
[SOUR]:LIST:CURR:SLEW:POS [SOUR]:RES:TLEV TRIG:TIM
TRIG:SEQ2:COUN
21
3
Programming Examples
Introduction
This chapter contains examples on how to program your electronic load. Simple examples show you how
to program:
K Input functions such as voltage, current, and resistance
K Transient functions, including lists
K Measurement functions
K The status and protection functions
NOTE: These examples in this chapter show which commands are used to perform a particular
function, but do not show the commands being used in any particular programming
environment.
Programming the Input
Power-on Initialization
When the electronic load is first turned on, it wakes up with the input state set OFF. The following
commands are given implicitly at power-on:
*RST
*CLS
*SRE 0
*ESE 0
*RST is a convenient way to program all parameters to a known state. Refer to the *RST command in
chapter 4 to see how each programmable parameter is set by *RST. Refer to the *PSC command in
chapter 4 for more information on the power-on initialization of the *ESE and the *SRE registers.
Enabling the Input
To enable the input, use the command:
INPut ON
Input Voltage
The input voltage is controlled with the VOLTage command. For example, to set the input voltage to 25
volts, use:
VOLTage 25
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3 - Programming Examples
Maximum Voltage
The maximum input voltage that can be programmed can be queried with:
VOLTage? MAXimum
Input Current
All models have a programmable current function. The command to program the current is:
CURRent
where is the input current in amperes.
Maximum Current
The maximum input current that can be programmed can be queried with:
CURRent? MAXimum
Overcurrent Protection
The electronic load can also be programmed to turn off its input if the current protection level is reached.
As explained in chapter 4, this protection feature is implemented the following command:
CURRent:PROTection:STATe ON | OFF
NOTE: Use CURRent:PROTection:DELay to prevent momentary current limit conditions caused
by programmed input changes from tripping the overcurrent protection.
Setting the Triggered Voltage or Current Levels
To program voltage or current triggered levels, you must specify the voltage or current level that the input
will go to once a trigger signal is received. Use the following commands to set a triggered level:
VOLTage:TRIGgered or
CURRent:TRIGgered
NOTE: Until they are explicitly programmed, triggered levels will assume their corresponding
immediate levels. For example, if a electronic load is powered up and VOLTage:LEVel is
programmed to 6, then VOLTage:LEVel:TRIGger will also be 6 until you program it to
another value. Once you program VOLTage:LEVel:TRIGger to a value, it will remain at
that regardless of how you subsequently reprogram VOLTage:LEVel. Then, when the
trigger occurs, the VOLTage:LEVel is set to the VOLTage:LEVel:TRIGger value.
Generating Triggers
You can generate a single trigger by sending the following command over the GPIB:
TRIGger:IMMediate
Note that this command will always generate a trigger. Use the TRIGger:SOURce command to select
other trigger sources such as the mainframe's external trigger input.
24
Programming Examples - 3
Programming Transients
Transient operation is used to synchronize input changes with internal or external trigger signals, and
simulate loading conditions with precise control of timing, duration, and slew. The following transient
modes can be generated:
Continuous Generates a repetitive pulse stream that toggles between two load levels.
Pulse Generates an load change that returns to its original state after some time period.
Toggled Generates a repetitive pulse stream that toggles between two load levels. Similar to
Continuous mode except that the transient points are controlled by explicit triggers
instead of an internal transient generator.
NOTE: Before turning on transient operation, set the desired mode of operation as well as all of
the parameters associated with transient operation. At *RST all transient functions are set
to OFF.
Continuous Transients
In continuous operation, a repetitive pulse train switches between two load levels, a main level (which can
be either the immediate or triggered level) and a transient level. The rate at which the level changes is
determined by the slew rate (see slew rate descriptions for CV, CR, or CV mode as applicable). In
addition, the frequency and duty cycle of the continuous pulse train are programmable. Use the following
commands to program continuous transients:
TRANsient:MODE CONTinuous
CURRent 5
CURRent:TLEVel 10
TRANsient:FREQuency 1000
TRANsient:DCYCle 40
TRANsient ON
This example assumes that the CC mode is active and the slew rate is at the default setting (maximum
rate). The load module starts conduction at the main level (in this case 5 amps). When transient
operation is turned on (no trigger is required in continuous mode), the module input current will slew to
and remain at 10 amps for 40% of the period (400