Agilent Technologies 54621A Manual

Programmer’s Guide
Publication Number 54622-97038
September 2002
For Safety information see t e pages be ind t e Index.
© Copyrig t Agilent Tec nologies 2000-2002
All Rig ts Reserved
Agilent 54621A/22A/24A/41A/42A
Oscilloscopes and
Agilent 54621D/22D/41D/42D
Mixed- ignal Oscilloscopes

ii
Programming the Oscilloscope
W en you attac an interface module to t e rear of t e oscilloscope, it
becomes programmable. T at is, you can ook a controller (suc as a
PC or workstation) to it, and write programs on t at controller to
automate oscilloscope setup and data capture.
T e following figure s ows t e basic structure of every program you will
write for t e oscilloscope.
Initialize
To ensure consistent, repeatable performance, you need to start t e
program, controller, and oscilloscope in a known state. Wit out correct
initialization, your program may run correctly in one instance and not in
anot er. T is mig t be due to c anges made in configuration by previous
program runs or from t e front panel of t e oscilloscope.
• Program initialization defines and initializes variables, allocates
memory, or tests system configuration.
• Controller initialization ensures t at t e interface to t e oscilloscope
(eit er GPIB or RS-232) is properly set up and ready for data transfer.
• Oscilloscope initialization sets t e c annel configuration and labels,
t res old voltages, trigger specification and mode, timebase, and
acquisition type.

iii
Capture
Once you initialize t e oscilloscope, you can begin capturing data for
analysis. Remember t at w ile t e oscilloscope is responding to
commands from t e controller, it is not performing acquisitions. Also,
w en you c ange t e oscilloscope configuration, any data already
captured will most likely be rendered.
To collect data, you use t e :DIGitize command. T is command clears
t e waveform buffers and starts t e acquisition process. Acquisition
continues until acquisition memory is full, t en stops. T e acquired data
is displayed by t e oscilloscope, and t e captured data can be measured,
stored in trace memory in t e oscilloscope, or transferred to t e
controller for furt er analysis. Any additional commands sent w ile
:DIGitize is working are buffered until :DIGitize is complete.
You could also put t e oscilloscope into run mode, t en use a wait loop
in your program to ensure t at t e oscilloscope as completed at least
one acquisition before you make a measurement. Agilent does not
recommend t is because t e needed lengt of t e wait loop may vary,
causing your program to fail. :DIGitize, on t e ot er and, ensures t at
data capture is complete. Also, :DIGitize, w en complete, stops t e
acquisition process so t at all measurements are on displayed data, not
on a constantly c anging data set.
Analyze
After t e oscilloscope as completed an acquisition, you can find out
more about t e data, eit er by using t e oscilloscope measurements or
by transferring t e data to t e controller for manipulation by your
program. Built-in measurements include frequency, duty cycle, period,
and positive and negative pulse widt .
Using t e :WAVeform commands, you can transfer t e data to your
controller. You may want to display t e data, compare it to a known good
measurement, or simply c eck logic patterns at various time intervals in
t e acquisition.

iv
In This Book
T is Programmer’s Guide is your introduction to programming t e
oscilloscope using an instrument controller. T is book, wit t e Programmer’s
Reference, provides a compre ensive description of t e oscilloscope’s
programmatic interface. T e Programmer’s Reference is supplied as a
Microsoft Windows Help file on a 3.5" diskette.
T e oscilloscope as a built-in RS-232-C port for programming. To program t e
oscilloscope over GPIB, you need t e N2757A GPIB Interface Module. You also
need an instrument controller t at supports eit er t e IEEE-488 or RS-232-C
interface standards, and a programming language capable of communicating
wit t ese interfaces.
T is book contains t e following information:
Chapter 1 Introduction to Programming, gives a general overview of
oscilloscope programming.
Chapter 2 Programming Getting Started, s ows a simple program, explains
its operation, and discusses considerations for data types.
Chapter 3 GPIB, discusses t e general considerations for programming t e
instrument over an GPIB interface.
Chapter 4 Programming over RS-232-C, discusses t e general considerations
for programming t e instrument over an RS-232-C interface.
Chapter 5 Programming and Documentation Conventions, describes t e
conventions used in representing t e syntax of commands t roug out t is book
and t e Programmer’s Reference, and gives an overview of t e oscilloscope
command set.
Chapter 6 Status Reporting, discusses t e oscilloscope status registers and
ow to use t em in your programs.
Chapter 7 Installing and Using t e Programmer’s Reference, tells ow to
install t e Programmer’s Reference online elp file in Microsoft Windows, and
explains elp file navigation.
Chapter 8 Programmer’s Quick Reference, lists all t e commands and queries
available for programming t e oscilloscope.
For information on oscilloscope operation, see t e User’s Guide. For
information on interface configuration, see t e documentation for t e
oscilloscope interface module and t e interface card used in your controller (for
example, t e Agilent 82350A interface for IBM PC-compatible computers).

Contents
Contents-1
1 Introduction to Programming
Talking to t e Instrument 1-3
Program Message Syntax 1-4
Combining Commands from t e Same Subsystem 1-7
Duplicate Mnemonics 1-8
Query Command 1-9
Program Header Options 1-10
Program Data Syntax Rules 1-11
Program Message Terminator 1-13
Selecting Multiple Subsystems 1-14
2 Programming Getting tarted
Initialization 2-3
Autoscale 2-4
Setting Up t e Instrument 2-5
Example Program 2-6
Using t e DIGitize Command 2-7
Receiving Information from t e Instrument 2-9
String Variables 2-10
Numeric Variables 2-11
Definite-Lengt Block Response Data 2-12
Multiple Queries 2-13
Instrument Status 2-13
3 Programming over GPIB
Interface Capabilities 3-3
Command and Data Concepts 3-3
Addressing 3-4
Communicating Over t e Bus 3-5
Lockout 3-6
Bus Commands 3-6
4 Programming over R -232-C
Interface Operation 4-3
Cables 4-3
Minimum T ree-Wire Interface wit Software Protocol 4-4
Extended Interface wit Hardware Hands ake 4-5
Configuring t e Interface 4-6
Interface Capabilities 4-7
Lockout Command 4-8

Contents
Contents-2
5 Programming and Documentation Conventions
Command Set Organization 5-3
T e Command Tree 5-6
Obsolete and Discontinued Commands 5-10
Truncation Rules 5-15
Infinity Representation 5-16
Sequential and Overlapped Commands 5-16
Response Generation 5-16
Notation Conventions and Definitions 5-17
Program Examples 5-18
6 tatus Reporting
Status Reporting Data Structures 6-5
Status Byte Register (SBR) 6-8
Service Request Enable Register (SRER) 6-10
Trigger Event Register (TRG) 6-10
Standard Event Status Register (SESR) 6-11
Standard Event Status Enable Register (SESER) 6-12
Operation Status Register (OPR) 6-13
Arm Event Register (ARM) 6-13
Error Queue 6-14
Output Queue 6-15
Message Queue 6-15
Clearing Registers and Queues 6-15
7 Installing and Using the Programmer’s Reference
To install t e elp file under Microsoft Windows 7-3
To get updated elp and program files via t e Internet 7-4
To start t e elp file 7-5
To navigate t roug t e elp file 7-5
8 Programmer’s Quick Reference
Conventions 8-3
Suffix Multipliers 8-3
Commands and Queries 8-4

1
Introduction to Programming

1-2
Introduction to Programming
C apters 1 and 2 introduce t e basics for remote programming of an
oscilloscope. T e programming instructions in t is manual conform to
t e IEEE488.2 Standard Digital Interface for Programmable
Instrumentation. T e programming instructions provide t e means of
remote control.
To program t e oscilloscope you must add eit er a GPIB (N2757A)
interface, or program over t e built-in RS-232-C interface on t e rear
panel.
You can perform t e following basic operations wit a controller and an
oscilloscope:
• Set up t e instrument.
• Make measurements.
• Acquire data (waveform, measurements, configuration) from t e
oscilloscope.
• Send information (pixel images, configurations) to t e oscilloscope.
Ot er tasks are accomplis ed by combining t ese basic functions.
Languages for Program Examples
The programming examples for individual commands in this manual are written in
HPBASIC 6.3 or C.

1-3
Introduction to Programming
Talking to the Instrument
Talking to the Instrument
Computers acting as controllers communicate wit t e instrument by sending
and receiving messages over a remote interface. Instructions for programming
normally appear as ASCII c aracter strings embedded inside t e output
statements of a ost language available on your controller. T e input statements
of t e ost language are used to read in responses from t e oscilloscope.
For example, HPBASIC uses t e OUTPUT statement for sending commands
and queries. After a query is sent, t e response is usually read in using t e
ENTER statement.
Messages are placed on t e bus using an output command and passing t e
device address, program message, and terminator. Passing t e device address
ensures t at t e program message is sent to t e correct interface and
instrument.
T e following HP BASIC statement sends a command w ic turns on label
display.
OUTPUT < device address > ;":CHANNEL1:BWLIMIT ON"<terminator>
T e < device address > represents t e address of t e device being programmed.
Eac of t e ot er parts of t e above statement are explained in t e following
pages.

1-4
Introduction to Programming
Program Message Syntax
Program Message yntax
To program t e instrument remotely, you must understand t e command
format and structure expected by t e instrument. T e IEEE 488.2 syntax rules
govern ow individual elements suc as eaders, separators, program data, and
terminators may be grouped toget er to form complete instructions. Syntax
definitions are also given to s ow ow query responses are formatted. T e
following figure s ows t e main syntactical parts of a typical program
statement.
Figure 1-1
Program Message Syntax
Output Command
T e output command is entirely dependent on t e programming language.
T roug out t is manual, HPBASIC is used in most examples of individual
commands. If you are using ot er languages, you will need to find t e
equivalents of HP BASIC commands like OUTPUT, ENTER, and CLEAR to
convert t e examples. T e instructions listed in t is manual are always s own
between quotation marks in t e example programs.
Device Address
T e location w ere t e device address must be specified is also dependent on
t e programming language you are using. In some languages, t is may be
specified outside t e output command. In HP BASIC, t is is always specified
after t e keyword OUTPUT. T e examples in t is manual assume t e
oscilloscope is at device address 707 . W en writing programs, t e address
varies according to ow t e bus is configured.