Programmer’s Guide
Publication Number 54622-97001
May 2000
For Safety information, Warranties, and Regulatory information,
see the pages behind the Index.
© Copyright Agilent Technologies 2000
All Rights Reserved
54621A/22A/24A Oscilloscopes
and 54621D/22D
Mixed-Signal Oscilloscopes
Programming the Oscilloscope
When you attach an interface module to the rear of the oscilloscope, it
becomes programmable. That is, you can hook a controller (such as a
PC or workstation) to it, and write programs on that controller to
automate oscilloscope setup and data capture.
The following figure shows the basic structure of every program you will
write for the oscilloscope.
Initialize
To ensure consistent, repeatable performance, you need to start the
program, controller, and oscilloscope in a known state. Without correct
initialization, your program may run correctly in one instance and not in
another. This might be due to changes made in configuration by previous
program runs or from the front panel of the oscilloscope.
• Program initialization defines and initializes variables, allocates
memory, or tests system configuration.
• Controller initialization ensures that the interface to the oscilloscope
(either GPIB or RS-232) is properly set up and ready for data transfer.
• Oscilloscope initialization sets the channel configuration and labels,
threshold voltages, trigger specification and mode, timebase, and
acquisition type.
ii
Capture
Once you initialize the oscilloscope, you can begin capturing data for
analysis. Remember that while the oscilloscope is responding to
commands from the controller, it is not performing acquisitions. Also,
when you change the oscilloscope configuration, any data already
captured will most likely be rendered.
To collect data, you use the :DIGitize command. This command clears
the waveform buffers and starts the acquisition process. Acquisition
continues until acquisition memory is full, then stops. The acquired data
is displayed by the oscilloscope, and the captured data can be measured,
stored in trace memory in the oscilloscope, or transferred to the
controller for further analysis. Any additional commands sent while
:DIGitize is working are buffered until :DIGitize is complete.
You could also put the oscilloscope into run mode, then use a wait loop
in your program to ensure that the oscilloscope has completed at least
one acquisition before you make a measurement. HP does not
recommend this because the needed length of the wait loop may vary,
causing your program to fail. :DIGitize, on the other hand, ensures that
data capture is complete. Also, :DIGitize, when complete, stops the
acquisition process so that all measurements are on displayed data, not
on a constantly changing data set.
Analyze
After the oscilloscope has completed an acquisition, you can find out
more about the data, either by using the oscilloscope measurements or
by transferring the data to the controller for manipulation by your
program. Built-in measurements include frequency, duty cycle, period,
and positive and negative pulse width.
Using the :WAVeform commands, you can transfer the data to your
contro l ler. You may wa nt t o d isplay the da t a, c ompar e it to a known good
measurement, or simply check logic patterns at various time intervals in
the acquisition.
iii
In This Book
This Programmer’s Guide is your introduction to programming the
oscilloscope using an instrument controller. This book, with the Programmer’s
Reference, provides a comprehensive description of the oscilloscope’s
programmatic interface. The Programmer’s Reference is supplied as a
Microsoft Windows Help file on a 3.5" diskette.
The oscilloscope has a built-in RS-232-C port for programming. To program the
oscilloscope over GP-IB, you need the N2757A GPIB Interface Module. You also
need an instrument controller that supports either the IEEE-488 or RS-232-C
interface standards, and a programming language capable of communicating
with these interfaces.
This book contains the following information:
Chapter 1 Introduction to Programming, gives a general overview of
oscilloscope programming.
Chapter 2 Programming Getting Started, shows a simple program, explains
its operation, and discusses considerations for data types.
Chapter 3 GPIB, discusses the general considerations for programming the
instrument over an GPIB interface.
Chapter 4 P rogramming over RS-232-C, discus ses the general considerations
for programming the instrument over an RS-232-C interface.
Chapter 5 Programming and Documentation Conventions, describes the
conven ti o ns use d in repr e s enting the syn t ax of com m ands throu gh out this book
and the Programmer’s Reference, and gives an overview of the oscilloscope
command set.
Chapter 6 Status Reporting, discusses the oscilloscope status registers and
how to use them in your programs.
Chapter 7 Installing and Using the Programmer’s Reference, tells how to
install the Programmer’s Reference online help file in Microsoft Windows, and
explains help file navigation.
Chapter 8 Programmer’s Quick Reference, lists all the commands and queries
available for programming the oscilloscope.
For information on oscilloscope operation, see the User’s Guide. For
information on interface configuration, see the documentation for the
oscilloscope interface module and the interface card used in your controller (for
example, the HP82350A interface for IBM PC-compatible computers).
iv
Contents
1 Introduction to Programming
Talking to the Instrument 1-3
Program Message Syntax 1-4
Combining Commands from the 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 Started
Initialization 2-3
Autoscale 2-4
Setting Up the Instrument 2-5
Example Program 2-6
Using the DIGitize Command 2-7
Receiving Information from the Instrument 2-9
String Variables 2-10
Numeric Variables 2-11
Definite-Length 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 the Bus 3-5
Lockout 3-6
Bus Commands 3-6
4 Programming over RS-232-C
Interface Operation 4-3
Cables 4-3
Minimum Three-Wire Interface with Software Protocol 4-4
Extended Interface with Hardware Handshake 4-5
Configuring the Interface 4-7
Interface Capabilities 4-7
Communicating Over the RS-232-C Bus 4-8
Contents-1
Contents
5 Programming and Documentation Conventions
Command Set Organization 5-3
The Command Tree 5-6
Obsolete and Discontinued Commands 5-10
Truncation Rules 5-14
Infinity Representation 5-15
Sequential and Overlapped Commands 5-15
Response Generation 5-15
Notation Conventions and Definitions 5-16
Program Examples 5-17
6 Status 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
User Event Register (UER) 6-13
Local Event Register (LCL) 6-13
Operation Status Register (OPR) 6-13
Limit Test Event Register (LTER) 6-14
Mask Test Event Register (MTER) 6-15
Histogram Event Register (HER) 6-16
Arm Event Register (ARM) 6-16
Error Queue 6-17
Output Queue 6-18
Message Queue 6-18
Key Queue 6-18
Clearing Registers and Queues 6-18
7 Installing and Using the Programmer’s Reference
To install the help file under Microsoft Windows 7-3
To get updated help and program files via the Internet 7-4
To start the help file 7-5
To navigate through the help file 7-5
8 Programmer’s Quick Reference
Conventions 8-3
Suffix Multipliers 8-3
Commands and Queries 8-4
Contents-2
1
Introduction to Programming
Introduction to Programming
Chapters 1 and 2 introduce the basics for remote programming of an
oscilloscope. The programming instructions in this manual conform to
the IEEE488.2 Standard Digital Interface for Programmable
Instrumentation. The programming instructions provide the means of
remote control.
To program the oscilloscope you must add either a GPIB (N2757A)
interface, or program over the built-in RS-232-C interface on the rear
panel.
You can perform the following basic operations with a controller and an
oscilloscope:
• Set up the instrument.
• Make measurements.
• Acquire data (waveform, measurements, configuration) from the
oscilloscope.
• Send information (pixel images, configurations) to the oscilloscope.
Other tasks are accomplished by combining these basic functions.
Languages for Program Examples
The programming examples for individual commands in this manual are written in
HPBASIC 6.3 or C.
1-2
Introduction to Programming
Talking to the Instrument
Talking to the Instrument
Computers acting as controllers communicate with the instrument by sending
and receiving messages over a remote interface. Instructions for programming
normally appear as ASCII character strings embedded inside the output
statements of a host language available on your controller. The input statements
of the host language are used to read in responses from the oscilloscope.
For example, HPBASIC uses the OUTPUT statement for sending commands
and queries. After a query is sent, the response is usually read in using the
ENTER statement.
Messages are placed on the bus using an output command and passing the
device address, program message, and terminator. Passing the device address
ensures that the program message is sent to the correct interface and
instrument.
The following HP BASIC statement sends a command which turns on label
desplay.
OUTPUT < device address > ;":CHANNEL1:BWLIMIT ON"<terminator>
The < dev ice ad d r ess > rep r e sents t h e add ress o f the devi c e bei n g pr ogramme d .
Each of the other parts of the above statement are explained in the following
pages.
1-3
Figure 1-1
Introduction to Programming
Program Message Syntax
Program Message Syntax
To program the instrument remotely, you must understand the command
format and structure expected by the instrument. The IEEE 488.2 syntax rules
govern how individual elements such as headers, separators, program data, and
terminators may be grouped together to form complete instructions. Syntax
definitions are also given to show how query responses are formatted. The
following figure shows the main syntactical parts of a typical program
statement.
Program Message Syntax
Output Command
The output command is entirely dependent on the programming language.
Throughout this manual, HPBASIC is used in most examples of individual
commands. If you are using other languages, you will need to find the
equivalents of HP BASIC commands like OUTPUT, ENTER, and CLEAR to
convert the examples. The instructions listed in this manual are always shown
between quotation marks in the example programs.
Device Address
The location where the device address must be specified is also dependent on
the programming language you are using. In some languages, this may be
specified outside the output command. In HP BASIC, this is always specified
after the keyword OUTPUT. The examples in this manual assume the
oscilloscope is at device address 707 . When writing programs, the address
varies according to how the bus is configured.
1-4
Introduction to Programming
Program Message Syntax
Instructions
Instructions (both commands and queries) normally appear as a string
embedded in a statement of your host language, such as BASIC, Pascal, or C.
The only time a parameter is not meant to be expressed as a string is when the
instruction’s syntax definition specifies <block data>, such as <learnstring>.
There are only a few instructions that use block data.
Instructions are composed of two main parts:
• The header, which specifies the command or query to be sent.
• The program data, which provide additional information needed to clarify
the meaning of the instruction.
Instruction Header
The instruction header is one or more mnemonics separated by colons (:) that
represent the operation to be performed by the instrument. The command tree
in chapter 5 illustrates how all the mnemonics can be joined together to form a
complete header (see chapter 5, “Programming and Documentation
Conventions”).
The example in Figure 1-1 is a command. Queries are indicated by adding a
question mark (?) to the end of the header. Many instructions can be used as
either commands or queries, depending on whether or not you have included
the question mark. The command and query forms of an instruction usually
have different program data. Many queries do not use any program data.
White Space (Separator)
White space is used to separate the instruction header from the program data.
If the instruction does not require any program data parameters, you do not
need to include any white space. In this manual, white space is defined as one
or more space characters. ASCII defines a space to be character 32 (in decimal).
Program Data
Program data are used to clarify the meaning of the command or query. They
provide necessary information, such as whether a function should be on or off,
or which waveform is to be displayed. Each instruction’s syntax definition shows
the program data, as well as the values they accept. The section “Program Data
Syntax Rules” in this chapter has all of the general rules about acceptable values.
When there is more than one data parameter, they are separated by commas(,).
Spaces can be added around the commas to improve readability.
1-5
Introduction to Programming
Program Message Syntax
Header Types
There are three types of headers:
• Simple Command headers
• Compound Command headers
• Common Command headers
Simple Command Header Simple command headers contain a single
mnemonic. AUTOSCALE and DIGITIZE are examples of simple command
headers typically used in this instrument. The syntax is:
<program mnemonic><terminator>
Simple command headers must occur at the beginning of a program message;
if not, they must be preceded by a colon.
When program data must be included with the simple command header (for
example, :DIGITIZE CHANNEL1), white space is added to separate the data
from the header. The syntax is:
<program mnemonic><separator><program data><terminator>
Compound Command Header Compound command headers are a
combination of two program mnemonics. The first mnemonic selects the
subsystem, and the second mnemonic selects the function within that
subsystem. The mnemonics within the compound message are separated by
colons. For example:
To execute a single function within a subsystem:
:<subsystem>:<function><separator>
<program data><terminator>
(For example :CHANNEL1:BWLIMIT ON)
Common Command Header Common command headers control IEEE
488.2 functions within the instrument (such as clear status). Their syntax is:
*<command header><terminator>
No space or separator is allowed between the asterisk (*) and the command
header. *CLS is an example of a common command header.
1-6
Introduction to Programming
Combining Commands from the Same Subsystem
Combining Commands from the Same Subsystem
To execute more than one function within the same subsystem, separate the
functions with a semicolon (;):
:<subsystem>:<function><separator><data>;
<function><separator><data><terminator>
(For example :CHANNEL1:COUPLING DC;BWLIMIT ON)
1-7
Introduction to Programming
Duplicate Mnemonics
Duplicate Mnemonics
Identical function mnemonics can be used in more than one subsystem. For
example, the function mnemonic RANGE may be used to change the vertical
range or to change the horizontal range:
:CHANNEL1:RANGE .4
sets the vertical range of channel 1 to 0.4 volts full scale.
:TIMEBASE:RANGE 1
sets the horizontal time base to 1 second full scale.
CHANNEL1 and TIMEBASE are subsystem selectors and determine which
range is being modified.
1-8
Introduction to Programming
Query Command
Query Command
Command headers immediately followed by a question mark (?) are queries.
After receiving a query, the instrument interrogates the requested function and
places the answer in its output queue. The answer remains in the output queue
until it is read or another command is issued. When read, the answer is
transmitted across the bus to the designated listener (typically a controller).
For example, the query :TIMEBASE:RANGE? places the current time base
setting in the output queue. In HP BASIC, the controller input statement:
ENTER < device address > ;Range
passes the value across the bus to the controller and places it in the variable
Range.
Query commands are used to find out how the instrument is currently
configured. They are also used to get results of measurements made by the
instrument. For example, the command :MEASURE:RISETIME? instructs the
instrument to measure the rise time of your waveform and places the result in
the output queue.
The output queue must be read before the next program message is sent. For
example, when you send the query :MEASURE:RISETIME? you must follow
that query with an input statement. In HP BASIC, this is usually done with an
ENTER statement immediately followed by a variable name. This statement
reads the result of the query and places the result in a specified variable.
Read the Query Result First
Sending another command or query before reading the result of a query clears the
output buffer and the current response. It also generates a query interrupted error
in the error queue.
1-9
Introduction to Programming
Program Header Options
Program Header Options
You can send program headers using any combination of uppercase or lowercase
ASCII characters. Instrument responses, however, are always returned in
uppercase.
Program command and query headers may be sent in either long form (complete
spelling), short form (abbreviated spelling), or any combination of long form
and short form.
TIMEBASE:DELAY 1US - long form
TIM:DEL 1US - short form
Programs written in long form are easily read and are almost self-documenting.
The short form syntax conserves the amount of controller memory needed for
program storage and reduces I/O activity.
Command Syntax Programming Rules
The rules for the short form syntax are shown in chapter 5, “Programming and
Documentation Conventions.”
1-10
Introduction to Programming
Program Data Syntax Rules
Program Data Syntax Rules
Program data is used to convey a parameter information related to the command
header. At least one space must separate the command header or query header
from the program data.
<program mnemonic><separator><data><terminator>
When a program mnemonic or query has multiple program data, a comma
separates sequential program data.
<program mnemonic><separator><data>,<data><terminator>
For example, :CHANNEL:THRESHOLD POD1,TTL has two program data:
POD1 and TTL.
Two main types of program data are used in commands: character and numeric.
Character Program Data
Character program data is used to convey parameter information as alpha or
alphanumeric strings. For example, the :TIMEBASE:MODE command can be
set to normal, delayed, XY, or ROLL. The character program data in this case
may be NORMAL, DELAYED, XY, or roll. The command :TIMEBASE:MODE
DELAYED sets the time base mode to delayed.
The available mnemonics for character program data are always included with
the instruction’s syntax definition. See the online Programmer’s Reference for
more information. When sending commands, you may either the long form or
short form (if one exists). Uppercase and lowercase letters may be mixed freely.
When receiving query responses, uppercase letters are used exclusively.
Numeric Program Data
Some command headers require program data to be expressed numerically. For
example, :TIMEBASE:RANGE requires the desired full scale range to be
expressed numerically.
For numeric program data, you have the option of using exponential notation
or using suffix multipliers to indicate the numeric value. The following numbers
are all equal:
28 = 0.28E2 = 280e-1 = 28000m = 0.028K = 28e-3K.
When a syntax definition specifies that a number is an integer, that means that
the number should be whole. Any fractional part be ignored, truncating the
number. Numeric data parameters accept fractional values are called real
numbers.
1-11
Introduction to Programming
Program Data Syntax Rules
All numbers must be strings of ASCII characters. Thus, when sending the
number 9, you would send a byte repre sentin g the ASCII code for the character
9 (which is 57). A three-digit number like 102 would take up three bytes (ASCII
codes 49, 48, an d 50 ). Th i s is ha n d led a u tomati c a ll y w h e n yo u inc l u de th e enti r e
instruction in a string.
Embedded Strings
Embedded strings contain groups of alphanumeric characters, which are
treated as a uni t of da t a by th e os c illoscope . Fo r exam p le, t h e lin e of te x t wri tt e n
to the advisory line of the instrument with the :SYSTEM:DSP command:
:SYSTEM:DSP "This is a message."
Embedded strings may be delimited with either single (’) or double () quotes.
These strings are case-sensitive, and spaces act as legal characters just like any
other character.
1-12
Introduction to Programming
Program Message Terminator
Program Message Terminator
The program instructions within a data message are executed after the program
message terminator is received. The terminator may be either an NL (New Line)
character, an EOI (End-Or-Identify) asserted in the GPIB interface, or a
combination of the two. Asserting the EOI sets the EOI control line low on the
last byte of the data message. The NL character is an ASCII linefeed (decimal
10).
New Line Terminator Functions
The NL (New Line) terminator has the same function as an EOS (End Of String) and
EOT (End Of Text) terminator.
1-13
Introduction to Programming
Selecting Multiple Subsystems
Selecting Multiple Subsystems
You can send multiple program commands and program queries for different
subsystems on the same line by separating each command with a semicolon.
The colon following the semicolon enables you to enter a new subsystem. For
example:
<program mnemonic><data>;
:<program mnemonic><data><terminator>
:CHANNEL1:RANGE 0.4;:TIMEBASE:RANGE 1
Combining Compound and Simple Commands
Multiple commands may be any combination of compound and simple commands.
1-14
2
Programming Getting Started
Programming Getting Started
Th is ch a pte r ex pl ain s ho w to s et up t he in st ru men t , h ow to r et rie ve se tu p
information and measurement results, how to digitize a waveform, and
how to pass data to the controller.
Languages for Programming Examples
The programming examples in this manual are written in HPBASIC 6.3 or C.
2-2
Programming Getting Started
Initialization
Initialization
To make sure the bus and all appropriate interfaces are in a known state, begin
every program with an initialization statement. HP BASIC provides a CLEAR
command which clears the interface buffer:
CLEAR 707 ! initializes the interface of the instrument
When you are using GPIB, CLEAR also resets the oscilloscope’s parser. The
parser is the program which reads in the instructions which you send it.
After clearing the interface, initialize the instrument to a preset state:
OUTPUT 707;"*RST" ! initializes the instrument to a preset
state.
Information for Initializing the Instrument
The actual commands and syntax for initializing the instrument are discussed in the
common commands section of the online Programmer’s Reference.
Refer to your controller manual and programming language reference manual for
information on initializing the interface.
2-3
Programming Getting Started
Autoscale
Autoscale
The AUTOSCALE feature performs a very useful function for unknown
waveforms by setting up the vertical channel, time base, and trigger level of the
instrument.
The syntax for the autoscale function is:
:AUTOSCALE<terminator>
2-4
Programming Getting Started
Setting Up the Instrument
Setting Up the Instrument
A typical oscilloscope setup would set the vertical range and offset voltage, the
horizontal range, delay time, delay reference, trigger mode, trigger level, and
slope. An example of the commands that might be sent to the oscilloscope are:
:CHANNEL1:PROBE 10;RANGE 16;OFFSET 1.00<terminator>
:TIMEBASE:MODE NORMAL;RANGE 1E-3;DELAY 100E-6<terminator>
Vertical is set to 16V full-scale (2 V/div) with center of screen at 1V and probe
attenuation set to 10. This example sets the time base at 1 ms full-scale
(100 ms/div) with a delay of 100 ms.
2-5
Programming Getting Started
Example Program
Example Program
This program demonstrates the basic command structure used to program the
oscilloscope.
10 CLEAR 707 ! Initialize instrument interface
20 OUTPUT 707;"*RST" ! Initialize inst to preset state
30 OUTPUT 707;":TIMEBASE:RANGE 5E-4" ! Time base to 50 us/div
40 OUTPUT 707;":TIMEBASE:DELAY 0" ! Delay to zero
50 OUTPUT 707;":TIMEBASE:REFERENCE CENTER" ! Display reference at center
60 OUTPUT 707;":CHANNEL1:PROBE 10" ! Probe attenuation to 10:1
70 OUTPUT 707;":CHANNEL1:RANGE 1.6" ! Vertical range to 1.6 V full scale
80 OUTPUT 707;":CHANNEL1:OFFSET -.4" ! Offset to -0.4
90 OUTPUT 707;":CHANNEL1:COUPLING DC" ! Coupling to DC
100 OUTPUT 707;":TRIGGER:SWEEP NORMAL" ! Normal triggering
110 OUTPUT 707;":TRIGGER:LEVEL -.4" ! Trigger level to -0.4
120 OUTPUT 707;":TRIGGER:SLOPE POSITIVE" ! Trigger on positive slope
130 OUTPUT 707;":ACQUIRE:TYPE NORMAL" ! Normal acquisition
140 END
• Line 10 initializes the instrument interface to a known state.
• Line 20 initializes the instrument to a preset state.
• Lines 30 through 50 set the time base mode to normal with the horizontal
time at 50 ms/div with 0 s of delay referenced at the center of the graticule.
• Lines 60 through 90 set the vertical range to 1.6 volts full scale with center
screen at -0.4 volts with 10:1 probe attenuation and DC coupling.
• Lines 100 through 120 configure the instrument to trigger at -0.4 volts with
normal triggering.
• Line 130 configures the instrument for normal acquisition.
2-6
Programming Getting Started
Using the DIGitize Command
Using the DIGitize Command
The DIGitize command is a macro that captures data satisfying the
specifications set up by the ACQuire subsystem. When the digitize process is
complete, the acquisition is stopped. The captured data can then be measured
by the instrument or transferred to the controller for further analysis. The
captured data consists of two parts: the waveform data record and the preamble.
Ensure New Data is Collected
When you change the oscilloscope configuration, the waveform buffers are cleared.
Before doing a measurement, send the DIGitize command to the oscilloscope to
ensure new data has been collected.
When you send the DIGitize command to the oscilloscope, the specified channel
signal is digitized with the current ACQuire parameters. To obtain waveform
data, you must specify the WAVEFORM parameters for the waveform data prior
to sending the :WAVEFORM:DATA? query.
Set :TIMebase:MODE to NORMal when using :DIGitize
:TIMebase:MODE must be set to NORMal to perform a :DIGitize command or to
perform any WAVeform subsystem query. A "Settings conflict" error message will be
returned if these commands are executed when MODE is set to ROLL, XY, or
DELayed. Sending the *RST (reset) command will also set the time base mode to
normal.
The number of data points comprising a waveform varies according to the
number requested in the ACQuire subsystem. The ACQuire subsystem
determines the number of data points, type of acquisition, and number of
averag e s us e d by th e DIGit i ze com m a nd. T h is a l l ows y o u to spec i f y e x a c tly wh a t
the digitized information contains.
2-7
Programming Getting Started
Using the DIGitize Command
The following program example shows a typical setup:
OUTPUT 707;":ACQUIRE:TYPE AVERAGE"<terminator>
OUTPUT 707;":ACQUIRE:COMPLETE 100"<terminator>
OUTPUT 707;":WAVEFORM:SOURCE CHANNEL1"<terminator>
OUTPUT 707;":WAVEFORM:FORMAT BYTE"<terminator>
OUTPUT 707;":ACQUIRE:COUNT 8"<terminator>
OUTPUT 707;":WAVEFORM:POINTS 500"<terminator>
OUTPUT 707;":DIGITIZE CHANNEL1"<terminator>
OUTPUT 707;":WAVEFORM:DATA?"<terminator>
This setup places the instrument into the averaged mode with eight averages.
This means that when the DIGitize command is received, the command will
execute until the signal has been averaged at least eight times.
After receiving the :WAVEFORM:DATA? query, the instrument will start passing
the waveform information when addressed to talk.
Di g it ize d w av ef o r m s a re pa ss ed fr o m t he in str u m e n t t o t h e c o n tr ol l er by se nd i ng
a numerical representation of each digitized point. The format of the numerical
representation is controlled with the :WAVEFORM:FORMAT command and may
be selected as BYTE, WORD, or ASCII.
The easiest method of transferring a digitized waveform depends on data
structures, formatting available and I/O capabilities. You must scale the integers
to determine the voltage value of each point. These integers are passed starting
with the leftmost point on the instrument’s display. For more information, see
the waveform subsystem commands and corresponding program code examples
in the online Programmer’s Reference.
Aborting a Digitize Operation Over GPIB
When using GPIB, you can abort a digitize operation by sending a Device Clear over
the bus (CLEAR 707).
2-8
Programming Getting Started
Receiving Information from the Instrument
Receiving Information from the Instrument
After receiving a query (command header followed by a question mark), the
instrument interrogates the requested function and places the answer in its
output queue. The answer remains in the output queue until it is read or another
command is issued. When read, the answer is transmitted across the interface
to the designated listener (typically a controller). The input statement for
receiving a response message from an instrument’s output queue typically has
two parameters; the device address, and a format specification for handling the
response message. For example, to read the result of the query command
:CHANNEL1:COUPLING? you would execute the HP BASIC statement:
ENTER <device address> ;Setting$
where <device address> represents the address of your device. This would
enter the current setting for the channel one coupling in the string variable
Setting$.
All results for queries sent in a program message must be read before another
program message is sent. For example, when you send the query
:MEASURE:RISETIME?, you must follow that query with an input statement.
In HP BASIC, this is usually done with an ENTER statement.
Sending another command before reading the result of the query clears the
output buffer and the current response. This also causes an error to be placed
in the error queue.
Executing an input statement before sending a query causes the controller to
wait indefinitely.
The format specification for handling response messages is dependent on both
the controller and the programming language.
2-9
Programming Getting Started
String Variables
String Variables
The output of the instrument may be numeric or character data depending on
what is queried. Refer to the specific commands for the formats and types of
data returned from queries.
Express String Variables Using Exact Syntax
In HP BASIC 6.3, string variables are case sensitive and must be expressed exactly
the same each time they are used.
Address Varies According to Configuration
For the example programs in the help file, assume that the device being programmed
is at device address 707. The actual address varies according to how you configured
the bus for your own application.
The following example shows the data being returned to a string variable:
10 DIM Rang$[30]
20 OUTPUT 707;":CHANNEL1:RANGE?"
30 ENTER 707;Rang$
40 PRINT Rang$
50 END
After running this program, the controller displays:
+40.0E-00
2-10
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