Agilent 8702D Programmers Guide

Programmer’s Guide

HP 8702D
Lightwave Component Analyzer

© Copyright Hewlett-Packard
Company 1997
All Rights Reserved. Repro­duction, adaptation, or trans­lation without prior written
permission is prohibited,
except as allowed under copy­right laws.

HP Part No. 08702-90042
Printed in USA
April 1997

Hewlett-Packard Company
Lightwave Operations
1400 Fountaingrove Parkway
Santa Rosa, CA 95403-1799,
USA
[phone]

Notice.

The information contained in
this document is subject to
change without notice. Com­panies, names, and data used
in examples herein are ficti­tious unless otherwise noted.
Hewlett-Packard makes no
warranty of any kind with
regard to this material, includ­ing but not limited to, the
implied warranties of mer­chantability and fitness for a
particular purpose. Hewlett­Packard shall not be liable for
errors contained herein or for
incidental or consequential
damages in connection with
the furnishing, performance,
or use of this material.

Restricted Rights Legend.

Use, duplication, or disclo­sure by the U.S. Government
is subject to restrictions as set
forth in subparagraph (c) (1)
(ii) of the Rights in Technical
Data and Computer Software
clause at DFARS 252.227-7013
for DOD agencies, and sub­paragraphs (c) (1) and (c) (2)
of the Commercial Computer
Software Restricted Rights
clause at FAR 52.227-19 for
other agencies.

Safety Symbols.

CAUTION

The

caution

sign denotes a
hazard. It calls attention to a
procedure which, if not cor­rectly performed or adhered
to, could result in damage to
or destruction of the product.
Do not proceed beyond a cau­tion sign until the indicated
conditions are fully under­stood and met.

WARNING

The

warning

sign denotes a
hazard. It calls attention to a
procedure which, if not cor­rectly performed or adhered
to, could result in injury or
loss of life. Do not proceed
beyond a warning sign until
the indicated conditions are
fully understood and met.

The instruction man­ual symbol. The prod­uct is marked with this
warning symbol when
it is necessary for the
user to refer to the
instructions in the
manual.

The laser radiation
symbol. This warning
symbol is marked on
products which have a
laser output.

The AC symbol is used
to indicate the
required nature of the
line module input
power.

The ON symbols are

|

used to mark the posi­tions of the instrument
power line switch.

The OFF symbols

❍

are used to mark the
positions of the instru­ment power line
switch.

The CE mark is a reg­istered trademark of
the European Commu­nity.

The CSA mark is a reg­istered trademark of
the Canadian Stan­dards Association.

This text denotes the

ISM1-A

instrument is an
Industrial Scientific
and Medical Group 1
Class A product.

Typographical Conven­tions.

The following conventions are
used in this book:

Key type

for keys or text
located on the keyboard or
instrument.

Softkey type

for key names that
are displayed on the instru­ment’s screen.

Display type

for words or
characters displayed on the
computer’s screen or instru­ment’s display.

User type

for words or charac-

ters that you type or enter.

Emphasis

type for words or
characters that emphasize
some point or that are used as
place holders for text that you
type.

ii

The HP 8702D—At a Glance

The HP 8702D—At a Glance

HP 8702D Programmer’s Guide

The
ment. The programming syntax conforms to the

tal Interface for Programmable Instrumentation

Chapter 1, “Writing Programs” provides information on addressing the instru­ment, debugging programs, and other important tasks. Each programming
command is documented in Chapter 3, “Language Reference”. Chapter 4,
“Graphics Language Reference” documents graphics commands for drawing
objects on the display. Refer to Chapter 2, “Examples” for a list of practical
examples using common measurement tasks.

shows you how to program the instru-

IEEE 488.2 Standard Digi-

.

iii

The HP 8702D—At a Glance

iv

The HP 8702D—At a Glance iii

1 Writing Programs

General Information 1-4
Selecting the HP-IB Device Mode 1-9
Making Measurements 1-11
Reading Data 1-14
Data-Processing Chain 1-21
Controlling Command Execution 1-25
Calibrating for Measurements 1-27
Debugging Programs 1-30
Understanding File Names 1-31
Drawing Graphics on the Display 1-33
Monitoring the Instrument 1-34
Response to IEEE-488 Universal Commands 1-40

Contents

2 Examples

Preparing Measurement Settings 2-4
Verifying Measurement Settings 2-6
S11 1-Port Measurement Calibration 2-8
Full 2-Port Measurement Calibration 2-13
Data Transfer Using Markers 2-18
Data Transfer Using ASCII Format 2-22
Data Transfer Using Floating-Point Numbers 2-25
Data Transfer Using Frequency-Array Information 2-28
Data Transfer Using Internal Binary Format 2-32
Using Error Queue 2-34
Generating Interrupts 2-37
Power Meter Calibration 2-41
Using the Learn String 2-45
Reading Calibration Data 2-48
Using Instrument States 2-52
Setting a List Frequency Sweep 2-56
Selecting a Single Segment 2-61
Setting up Limit Lines 2-65
Performing Pass/Fail Tests 2-69
Operation Using Talker/Listener Mode 2-73

Contents-1

Contents

Controlling Peripherals 2-76
Printing Via the Serial Port 2-80
Plotting Data 2-83
Reading Plot Files from Disk 2-86
Reading ASCII Instrument Files 2-94

3 Language Reference

4 Graphics Language Reference

5 Tables and Charts

HP-IB Requirements 5-3
Programming Commands by Functional Group 5-8
Key Definitions 5-26

Contents-2

1

Writing Programs

Writing Programs

Writing Programs

Writing Programs

This chapter provides a general introduction to programming the HP 8702D. It
covers topics such as command syntax, addressing the instrument, initializing
the instrument, and returning measurement results to the computer.

Before you begin programming, you should first become proficient at making
manual measurements as explained in the
learn the techniques and softkey presses needed to make a measurement, you
can refer to Table 5-4, “Keys versus Programming Commands,” on page 5-26
to locate the equivalent programming command.

NOTE:

HP 8702D User’s Guide

. Once you

The HP 8702D conforms to IEEE 488.1 and IEC-625 standards for interfacing instruments.

1-2

What you’ll find in this chapter

General Information 1-4

To select the communication mode 1-8
To change the HP-IB address 1-8

Selecting the HP-IB Device Mode 1-9

To change the HP-IB device mode 1-10
Making Measurements 1-11
Reading Data 1-14
Data-Processing Chain 1-21
Controlling Command Execution 1-25
Calibrating for Measurements 1-27

To calibrate the instrument 1-27
Debugging Programs 1-30

To start debugging mode 1-30
Understanding File Names 1-31
Drawing Graphics on the Display 1-33
Monitoring the Instrument 1-34
Response to IEEE-488 Universal Commands 1-40

Writing Programs

Writing Programs

1-3

Writing Programs

General Information

General Information

The HP 8702D occupies two HP-IB addresses: the instrument itself and the
display. The display address is derived from the instrument address as
described in “Drawing Graphics on the Display” on page 1-33. These addresses
are stored in short-term, non-volatile memory and are not affected when you

PRESET

press
device 16, and the display address is device 17.

There is also an address for the system controller. This address refers to the
controller when the HP 8702D is being used in pass-control mode. This is the
address that control is passed back to when the HP 8702D-controlled opera­tion is complete.

You can change the HP-IB address from the front panel as described in “To
change the HP-IB address” on page 1-8.

or cycle the power. The default address for the HP 8702D is

HP-IB status lights

When the HP 8702D is connected to the HP-IB, the front-panel HP-IB status
lights indicate the current status of the HP 8702D. These lights have the fol­lowing definitions:

R = Remote operation

L = Listen mode

T = Talk mode

S = Service request (SRQ) asserted by the HP 8702D

Remote mode and front-panel lockout

Whenever the instrument is controlled by a computer, the front-panel HP-IB
remote status light, R, is turned on, and the instrument keys are disabled.
Press the

Consult the documentation for your programming environment to determine
which commands are used to put an instrument in the remote and local lock­out modes. These are not HP 8702D commands; they control HP-IB control
lines and do not send any characters to the HP 8702D.

1-4

LOCAL

key to restore front panel control of the instrument.

Writing Programs

General Information

Initialize the instrument at the start of every program

It is good practice to initialize the instrument at the start of every program.
This ensures that the bus and all appropriate interfaces are in a known state.
HP BASIC provides a CLEAR command which clears the interface buffer and
also resets the instrument’s parser. (The parser is the program that reads the
instructions that you send.) Whenever the instrument is under remote pro­gramming control, it should be in the single measurement acquisition mode.
This is automatically accomplished when the RST is used. The RST command
initializes the instrument to the factory preset state:

CLEAR 716
OUTPUT 716;”RST”

Notice in the example above, that the commands are sent to an instrument
address of 716. This indicates address 16 on an interface with select code 7.
Pressing the

SET

key resets the instrument to either the factory preset state or a user-

PRESET

key does not change the HP-IB address. Pressing the

PRE-

defined preset state.

Rules for writing commands

The HP 8702D accepts letters, changing lowercase to uppercase, numbers,
decimal points, +, –, semicolons, carriage returns and line feeds. Leading
zeros, spaces, carriage returns, and unnecessary terminators are ignored,
except when inserted between a command and a numerical or string argu­ment. If the analyzer does not recognize a character as appropriate, it gener­ates a syntax error message and recovers at the next terminator.

For example, the CHAN command must be entered as CHAN1 or CHAN2.
Inserting a space in the syntax (CHAN 1) results in an error. However, a space
must be entered between the MARK2 command and its argument. For exam­ple, MARK2 1.4GHZ.

Units and terminators

The HP 8702D outputs data in basic units and assumes these basic units when
it receives an input (unless the input is otherwise qualified). The basic units
and allowable expressions can be found below. Both uppercase and lowercase
letters are acceptable.

1-5

Writing Programs

General Information

Table 1-1. Terminator Codes

S Seconds HZ Hertz

MS Milliseconds KHZ Kilohertz

US Microseconds MHZ Megahertz

NS Nanoseconds GHZ Gigahertz

PS Picoseconds DB dB or dBm

FS Femtoseconds V Volts

Terminators are used to indicate the end of a command. This allows the
HP 8702D to recover to the next command in the event of a syntax error. The
semicolon (;) is the recommended command terminator. The line-feed charac­ter (LF) and the HP-IB EOI line can also be used as terminators. Again, the
HP 8702D will ignore the carriage-return character (CR).

1-6

General Information

.

Table 1-2. HP-IB Interface Capabilities

Capability Description

SH1 Full-source handshake.

AH1 Full-acceptor handshake.

T6 Basic talker, answers serial poll, unaddresses if MLA is issued. No talk-only mode.

L4 Basic listener, unaddresses if MTA is issued. No listen-only mode.

SR1 Complete service request (SRQ) capabilities.

RL1 Complete remote/local capability including local lockout.

PP0 Does not respond to parallel poll.

DC1 Complete device clear.

DT1 Responds to a Group Execute Trigger (GET) in the hold-trigger mode.

Writing Programs

C1,C2,C3 System controller capabilities in system-controller mode.

C10 Pass control capabilities in pass-control mode.

E2 Tri-state drivers.

LE0 No extended listener capabilities.

TE0 No extended talker capabilities.

1-7

Writing Programs

General Information

To select the communication mode

1

Press the

2

Press

LOCAL

key.

TALKER/LISTENER

so that this softkey is underlined.

To change the HP-IB address

1

Press the

2

Press

3

Press

4

Use the front-panel knob or keys to enter the new HP-IB address.

LOCAL

key.

SET ADDRESSES.

ADDRESS: 8702

.

1-8

Writing Programs

Selecting the HP-IB Device Mode

Selecting the HP-IB Device Mode

Three different device modes are possible for the HP 8702D:

• talker/listener mode

• system-controller mode

• pass-control mode

Performing an instrument preset does not affect the selected bus mode,
although the bus mode will return to talker/listener mode if the line power is
cycled.

Tal k er /li st e ne r mo d e

This is the mode that is normally used for remote programming of the
HP 8702D. In talker/listener mode, the HP 8702D and all peripheral devices
are controlled from an external instrument controller. The controller can com­mand the HP 8702D to talk and other devices to listen. The HP 8702D and
peripheral devices cannot talk directly to each other unless the computer sets
up a data path between them. This mode allows the HP 8702D to act as either
a talker or a listener, as required by the controlling computer for the particular
operation in progress.

While in this mode, the HP 8702D can make a plot or print using the

PLOT;

addressed to talk by the system controller and then dump the display to a
plotter/printer that the system controller has addressed to listen. Use of the
commands
controller.

OUTPPRIN;

or

PLOT;

commands. The HP 8702D will wait until it is

PRINALL;

and

require control to be passed to another

OUTP-

System-controller mode

Do not attempt to use this mode for programming. This mode allows the
HP 8702D to control peripherals directly in a stand-alone environment (with­out an external controller). This mode can only be selected manually from the
HP 8702D’s front panel. It can only be used if no active computer or instru­ment controller is connected to the system via HP-IB. If an attempt is made to
set the HP 8702D to the system-controller mode when another controller is

1-9

Writing Programs

Selecting the HP-IB Device Mode

connected to the interface, the following message is displayed on the
HP 8702D’s display screen:

ON HP-IB"

The HP 8702D must be set to the system-controller mode in order to access
peripherals from the front panel. In this mode, the HP 8702D can directly con­trol peripherals (for example, plotters, printers, disk drives, and power
meters) and the HP 8702D may plot, print, store on disk or perform power
meter functions.

Pass-control mode

This mode allows the computer to control the HP 8702D via HP-IB (as with
the talker/listener mode), but also allows the HP 8702D to take control of the
interface in order to plot, print, or access a disk. During an HP 8702D-con­trolled peripheral operation, the host computer is free to perform other inter­nal tasks (for example, data or display manipulation) while the HP 8702D is
controlling the bus. After the HP 8702D-controlled task is completed, the
HP 8702D returns control to the system controller.

In pass-control mode, the HP 8702D can request control from the system con­troller and take control of the bus if the controller addresses it to take control.
This allows the HP 8702D to take control of printers, plotters, and disk drives
on an as-needed basis. The HP 8702D sets event-status-register bit 1 when it
needs control of the interface, and the HP 8702D will transfer control back to
the system controller at the completion of the operation. It will pass control
back to its controller address, specified by ADDRCONT.

.

"CAUTION: ANOTHER SYSTEM CONTROLLER

To change the HP-IB device mode

1

Press the

2

Press

1-10

LOCAL

key.

SET ADDRESSES.

Writing Programs

Making Measurements

Making Measurements

This section explains how to organize instrument commands into a measure­ment sequence. A typical measurement sequence consists of the following
steps:

1

Setting up the instrument

2

Calibrating the test setup

3

Connecting the device under test

4

Taking the measurement data

5

Post-processing the measurement data

6

Transferring the measurement data

Step 1. Setting up the instrument

Define the measurement by setting all of the basic measurement parameters.
These include:

• sweep type

• frequency span

• sweep time

• number of points (in the data trace)

• RF power level

• type of measurement

• IF averaging

• IF bandwidth

You can quickly set up an entire instrument state, using the save/recall regis­ters and the learn string. The learn string is a summary of the instrument state
compacted into a string that the computer reads and retransmits to the ana­lyzer. Refer to “Using the Learn String” on page 2-45.

1-11

Writing Programs

Making Measurements

Step 2. Calibrating the test setup

After you have defined an instrument state, you should perform a measure­ment calibration. Although it is not required for the measurement of O/E and
E/O devices, a measurement calibration is required to obtain useful measure­ments.

The following list describes several methods to calibrate the analyzer:

• Stop the program and perform a calibration from the analyzer’s front panel.

• Use the computer to guide you through the calibration, as discussed in “S11 1­Port Measurement Calibration” on page 2-8 and “Full 2-Port Measurement Cal­ibration” on page 2-13.

• Transfer the calibration data from a previous calibration back into the analyzer,
as discussed in “Using Instrument States” on page 2-52.

Step 3. Connecting the device under test

After you connect your test device, you can use the computer to speed up any
necessary device adjustments such as limit testing, bandwidth searches, and
trace statistics.

Step 4. Taking the measurement data

Measure the device response and set the analyzer to hold the data. This cap­tures the data on the analyzer display.

By using the single-sweep command (SING), you can insure a valid sweep.
When you use this command, the analyzer completes all stimulus changes
before starting the sweep, and does not release the HP-IB hold state until it
has displayed the formatted trace. Then when the analyzer completes the
sweep, the instrument is put into hold mode, freezing the data. Because single
sweep is OPC-compatible, it is easy to determine when the sweep has been
completed.

The number-of-groups command (NUMGn) triggers multiple sweeps. It is
designed to work the same as the single-sweep command. NUMGn is useful for
making a measurement with an averaging factor n (n can be 1 to 999). Both
the single-sweep and number-of-groups commands restart averaging.

1-12

Writing Programs

Making Measurements

Step 5. Post-processing the measurement data

Figure 1-1 on page 1-22 shows the process functions used to affect the data

after you have made an error-corrected measurement. These process func­tions have parameters that can be adjusted to manipulate the error-corrected
data prior to formatting. They do not affect the analyzer’s data gathering. The
most useful functions are trace statistics, marker searches, electrical-delay
offset, time domain, and gating.

After performing and activating a full 2-port measurement calibration, any of
the four S-parameters may be viewed without taking a new sweep.

Step 6. Transferring the measurement data

Read your measurement results. All the data-output commands are designed
toensure that the data transmitted reflects the current state of the instru­ment.

1-13

Writing Programs

Reading Data

Reading Data

Output queue

Whenever a output-data command is received, the HP 8702D puts the data
into the output queue (or buffer) where it is held until the system controller
outputs the next read command. The queue, however, is only one event long;
the next output-data command will overwrite the data already in the queue.
Therefore, it is important to read the output queue immediately after every
interrogation or data request from the HP 8702D.

Command interrogate

All instrument functions can be interrogated to find the current ON/OFF state
or value. For instrument state commands, append the question mark charac­ter (?) to the command to interrogate the state of the functions. Suppose the
operator has changed the power level from the HP 8702D’s front panel. The
computer can ascertain the new power level using the HP 8702D’s command­interrogate function. If a question mark is appended to the root of a command,
the HP 8702D will output the value of that function. For instance,

POWE 7 DB;

RF source power at the test port. When the HP 8702D receives
prepares to transmit the current RF source power level. This condition illumi­nates the HP 8702D front-panel talk light (T). In this case, the HP 8702D
transmits the output power level to the controller.

ON/OFF commands can be also be interrogated. The reply is a one (1) if the
function is ON or a zero (0) if it is OFF. For example, if a command controls an
active function that is underlined on the HP 8702D display, interrogating that
command yields a one (1) if the command is underlined or a zero (0) if it is
not. As another example, there are nine options on the format menu and only
one option is underlined at a time. Only the underlined option will return a
one (1) when interrogated. For instance, send the command string
the HP 8702D. If dual-channel display is switched ON, the HP 8702D will
return a one (1) to the instrument controller.

sets the source power to 7 dB, and

POWE?;

outputs the current

POWE?;

, it

DUAC?;

to

1-14

Writing Programs

Reading Data

Similarly, to determine if phase is being measured and displayed, send the
command string

PHAS?;

to the HP 8702D. In this case, the HP 8702D will
return a one (1) if phase is currently being displayed. Since the command only
applies to the active channel, the response to the

PHAS?;

query depends on

which channel is active.

Output syntax

The following three types of data are transmitted by the HP 8702D in ASCII
format:

• response to interrogation

• certain output commands

• ASCII floating-point (form 4) array transfers
Marker-output commands and interrogated commands are output in ASCII
format only, meaning that each character and each digit is transmitted as a
separate byte, leaving the receiving computer to reconstruct the numbers and
strings. Numbers are transmitted as 24-character strings, consisting of:

-DDD.DDDDDDDDDDDDDDDE-DD

When multiple numbers are sent, the numbers are separated by commas.

Table 1-3. Form 4 (ASCII) Data-Transfer Character Definitions

Character(s)* Definition

Sign – for negative, blank for positive.

3 digits Digits to the left of the decimal point.

Decimal point

15 digits Digits to the right of the decimal point.

E Exponent notation.

Sign – for negative, + (or blank) for positive.

Exponent Two digits for the exponent.

* The items in this column are separated by commas and delimited (terminated) with a line feed
character (LF).

1-15

Writing Programs

Reading Data

Marker data

The HP 8702D offers several options for outputting trace-related data. Trace
information can be read out of the HP 8702D in several different formats. Data
can be selectively read from the trace using the markers, or the entire trace
can be read by the controller. If only specific information is required (such as a
single point on the trace or the result of a marker search), the marker output
command can be used to read the information.

To read the trace data using the marker, the marker must first be assigned to
the desired frequency. This is accomplished using the marker commands. The
controller sends a marker command followed by a frequency within the trace­data range. If the actual desired frequency was not sampled, the markers can
be set to continuous mode and the desired marker value will be linearly inter­polated from the two nearest points. This interpolation can be prevented by
putting the markers into discrete mode. Discrete mode allows the marker to
only be positioned on a measured trace-data point.

As an alternative, the HP 8702D can be programmed to choose the stimulus
value by using the
or bandwidths search can be automatically determined with

MARKER SEARCH

function. Maximum, minimum, target value,

MARKER SEARCH

To continually update the search, switch the marker tracking ON. The trace­maximum search will remain activated until:

• The search is switched OFF

• The tracking is switched OFF

• All markers are switched OFF

.

Marker data can be output to a controller with a command to the HP 8702D.
This set of commands causes the HP 8702D to transmit three numbers:
marker value 1, marker value 2, and marker stimulus value. In log-magnitude
display mode we get the log magnitude at marker 1, zero, and the marker fre­quency. Refer to “Units as a Function of Display Format” on page 1-17 for a
complete listing of all the possibilities for values 1 and 2. The three possibili­ties for the third parameter are:

•frequency

• time (as in time domain)

• CW time

1-16

Table 1-4. Units as a Function of Display Format

OUTPMARK OUTPFORM Marker Readout

Display Format Marker Mode

Value 1 Value 2 Value 1 Value 2 Value

Writing Programs

Reading Data

AUX

Value

LOG MAG dB † dB † dB

PHASE degrees † degrees †

DELAY seconds † seconds †

SMITH CHART LIN MKR lin mag degrees real imag lin mag degrees

LOG MKR dB degrees real imag dB degrees

Re/Im real imag real imag real imag

R + jX real ohms imag ohms real imag real ohms imag ohms

G + jB real

Siemens

POLAR LIN MKR lin mag degrees real imag lin mag degrees

LOG MKR dB degrees real imag dB degrees

Re/Im real imag real imag real imag

LIN MAG lin mag † lin mag † lin mag †

REAL real † real † real

SWR SWR † SWR † SWR

* The marker readout values are the marker values displayed in the upper right-hand corner of the display. They also correspond to
the value and auxiliary value associated with the fixed marker.

†

Value 2 is not significant in this format, though it is included in data transfers.

imag

Siemens

real imag real

degrees †

seconds †

Siemens

†

imag

Siemens

†

†

1-17

Writing Programs

Reading Data

Array-data formats

The HP 8702D can transmit and receive arrays in the HP 8702D’s internal
binary format, as well as four different numeric formats. The current format is
set with the FORM command. This command does not affect learn-string
transfers, calibration-kit string transfers, or non-array transfers, such as com­mand interrogate, or output marker values. A transmitted array will be output
in the current format, and the HP 8702D will attempt to read incoming arrays
according to the current format. Each data point in an array is a pair of num­bers, usually a real/imaginary pair. The number of data points in each array is
the same as the number of points in the current sweep.

The five formats are described below:

1

The HP 8702D’s internal binary format, 6 bytes-per-data point. The array is
preceded by a four-byte header. The first two bytes represent the string
the standard block header. The second two bytes are an integer representing
the number of bytes in the block to follow. FORM 1 is best applied when rapid
data transfers, not to be modified by the computer nor interpreted by the user,
are required.

2

IEEE 32-bit floating-point format, 8 bytes-per-data point. The data is preceded
by the same header as in FORM 1. Each number consists of a 1-bit sign, an 8­bit biased exponent, and a 23-bit mantissa. FORM 2 is the format of choice if
your computer supports single-precision floating-point numbers.

"#A"

,

3

IEEE 64-bit floating-point format, 16 bytes-per-data point. The data is
preceded by the same header as in FORM 1. Each number consists of a 1-bit
sign, an 11-bit biased exponent, and a 52-bit mantissa. This format may be used
with double-precision floating-point numbers. No additional precision is
available in the HP 8702D data, but FORM 3 may be a convenient form for
transferring data to your computer.

4

ASCII floating-point format. The data is transmitted as ASCII numbers, as
described in “Output syntax” on page 1-15. There is no header. The HP 8702D
uses FORM 4 to transfer data that is not related to array transfers (for example,
marker responses and instrument settings).

5

PC-DOS 32-bit floating-point format with 4 bytes-per-number, 8 bytes-per-data
point. The data is preceded by the same header as in FORM 1. The byte order
is reversed to comply with PC-DOS formats.

controller, FORM 5 is the most effective format to use.

If you are using a PC-based

The HP 8702D terminates each transmission by asserting the EOI interface
line with the last byte transmitted. Table 1-5 on page 1-19 offers a comparative
overview of the five array-data formats.

1-18

Table 1-5. HP 8702D/Option 011 Array-Data Formats

Writing Programs

Reading Data

Format Type Type of Data

1 Internal Binary 3 6 1206 1210

2 IEEE 32-bit

Floating-Point

3 IEEE 64-bit

Floating-Point

4 ASCII Numbers 24 50 10,050 10,050

5 PC-DOS 32-bit

Floating-Point

a. There are two data values (real and imaginary) for every data point.
b. No header is used in form 4.

Bytes per Data

Value

4 8 1608 1612

8 16 3216 3220

4 8 1608 1612

Bytes per Data

Point

a

Bytes per 201

Point Trace

Trace-data transfers

Transferring trace data from the HP 8702D using an instrument controller can
be divided into three steps:

1

allocating an array to receive and store the data

2

commanding the HP 8702D to transmit the data

3

accepting the transferred data

Total Bytes

with Header

b

Data residing in the HP 8702D is always stored in pairs for each data point (to
accommodate real/imaginary pairs). The real value is first, followed by the
imaginary value. Hence, the receiving array has to be two elements wide, and
as deep as the number of points in the array being transferred. Memory space
for the array must be declared before any data can be transferred from the
HP 8702D to the computer. When reading logarithmic amplitude and phase,
save the first value of each data point pair and discard the second value.

As mentioned earlier, the HP 8702D can transmit data over HP-IB in five dif­ferent formats. The type of format affects what kind of data array is declared
(real or integer), because the format determines what type of data is trans­ferred. “Data Transfer Using Markers” on page 2-18 illustrates an ASCII trans­fer using Form 4. For more information on the various data formats, refer to
“Array-data formats” on page 1-18. For information on the various types of
data that can be obtained (raw data, error-corrected data, etc.), refer to “Data
levels” on page 1-23.

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Writing Programs

Reading Data

Frequency-related arrays

Frequency-related values are calculated for the HP 8702D displays. The only
data available to the programmer are the start and stop frequencies, or center
and span frequencies, of the selected frequency range.

In a linear frequency range, the frequency values can be easily calculated
because the trace data points are equally spaced across the trace. Relating the
data from a linear frequency sweep to frequency can be done by interrogating
the start frequency, the frequency span, and the number of points in the trace.

Given that information, the frequency of point n in a linear-frequency sweep is
represented by the equation:

F=Start frequency + (n–1) × Span/(Points–1)

In most cases, this is an easy solution for determining the related frequency
value that corresponds with a data point. This technique is illustrated in “Data
Transfer Using Markers” on page 2-18.

When using log sweep or a list-frequency sweep, the points are not evenly
spaced over the frequency range of the sweep. In these cases, the frequencies
can be read directly out of the instrument with the

OUTPLIML

command.
“Data Transfer Using Frequency-Array Information” on page 2-28 demon­strates this technique.

Executing

OUTPLIML;

reports the limit-test results by transmitting:

• the stimulus point tested

• a number indicating the limit-test results

• the upper test limit at the stimulus point (if available)

• the lower test limit at the stimulus point (if available)

The numbers used to indicate the limit-test results are:

• a negative one (–1) for no test

• a zero (0) for fail

• a positive one (1) for pass

If there are no limits available, the HP 8702D transmits zeros.

This data is very useful when testing with limit lines. It provides a method of
obtaining accurate frequency-stimulus values to correspond with the trace
data. The other limit-related values may be discarded and the stimulus values
used with the trace-data points.

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Writing Programs

Data-Processing Chain

Data-Processing Chain

This section describes the manner in which the HP 8702D processes measure­ment data. It includes information on data arrays, common output commands,
data levels, the learn string, and the calibration kit string.

Data arrays

Figure 1-1 on page 1-22 shows the different kinds of data available within the

instrument:

• raw measured data

• error-corrected data

• formatted data

• trace memory

• calibration coefficients

Trace memory can be directly output to a controller with
cannot be directly transmitted back.

OUTPMEMO;

, but it

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Writing Programs

Data-Processing Chain

Figure 1-1. The data-processing chain

All the data-output commands are designed to insure that the data transmit­ted reflects the current state of the instrument:

OUTPDATA, OUTPRAW

•

, and

OUTPFORM

will not transmit data until all format-

ting functions have completed.

OUTPLIML, OUTPLIMM

•

, and

OUTPLIMF

will not transmit data until the limit

test has occurred (if activated).

OUTPMARK

•

will activate a marker if a marker is not already selected. It will also
insure that any current marker searches have been completed before transmit­ting data.

OUTPMSTA

•

insures that the statistics have been calculated for the current trace
before transmitting data. If the statistics are not activated, it will activate the
statistics long enough to update the current values before deactivating the sta­tistics.

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Writing Programs

Data-Processing Chain

OUTPMWID

•

insures that a bandwidth search has been executed for the current
trace before transmitting data. If the bandwidth-search function is not activat­ed, it will activate the bandwidth-search function long enough to update the
current values before switching OFF the bandwidth-search functions.

Data levels

Different levels of data can be read out of the instrument. Refer to the data­processing chain in Figure 1-1 on page 1-22.

The following list describes the different types of data that are available from
the HP 8702D.

Raw data

Error-corrected
data

Formatted data

The basic measurement data, reflecting the stimulus parameters, IF averag­ing, and IF bandwidth. If a full 2-port measurement calibration is activated,
there are actually four raw arrays kept: one for each raw S-parameter. The
data can be output to a controller with the commands

OUTPRAW3, OUTPRAW4

. Normally, only raw 1 is available, and it holds the cur-

OUTPRAW1, OUTPRAW2

rent parameter. If a 2-port measurement calibration is active, the four arrays
refer to S

, S21, S12, and S22 respectively. This data is represented in real/

11

imaginary pairs.

This is the raw data with error-correction applied. The array represents the
currently measured parameter, and is stored in real/imaginary pairs. The
error-corrected data can be output to a controller with the
mand. The

OUTPMEMO;

command reads the trace memory, if available. The

OUTPDATA;

com-

trace memory also contains error-corrected data. Note that neither raw nor
error-corrected data reflect such post-processing functions as electrical-delay
offset, trace math, or time-domain gating.

This is the array of data actually being displayed. It reflects all post-processing
functions such as electrical delay and time domain. The units of the array out­put depend on the current display format. Refer to Table 1-4, “Units as a Func­tion of Display Format,” on page 1-17 for the various units defined as a
function of display format.

,

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Writing Programs

Data-Processing Chain

Calibration
coefficients

The results of a measurement calibration are arrays containing calibration
coefficients. These calibration coefficients are then used in the error-correc­tion routines. Each array corresponds to a specific error term in the error
model. The

HP 8702D User’s Guide

details which error coefficients are used
for specific calibration types, as well as the arrays those coefficients can be
found in. Not all calibration types use all 12 arrays. The data is stored as real/
imaginary pairs.

Generally, formatted data is the most useful of the four data levels, because it
is the same information the operator sees on the display. However, if post-pro­cessing is unnecessary (possibly in cases involving smoothing), error-cor­rected data may be more desirable. Error-corrected data also affords the user
the opportunity to input the data to the HP 8702D and apply post-processing
at another time.

Learn string and calibration-kit string

The learn string is a summary of the instrument state. It includes all the front­panel settings, the limit-test tables, and the list-frequency table for the cur­rent instrument state. It does not include calibration data or the information
stored in the save/recall registers.

The learn string can be output to a controller with the

OUTPLEAS;

execut­able, which commands the HP 8702D to start transmitting the binary string.
The string has a fixed length for a given firmware revision. It can not be more
than 3000 bytes in length. The array has the same header as in Form 1.

The calibration kit is a set of key characteristics of the calibration standards
used to increase the calibration accuracy. There are default kits for several dif­ferent connector types. There is also space for a user-defined calibration kit.
The command

OUTPCALK

outputs the currently active calibration kit as a
binary string in Form 1. As with the learn string, the calibration-kit string has a
fixed length for a given firmware revision. It can not be longer than
1000 bytes.

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