LeCroy 9410 Use and maintenance manual

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|I REMOTE CONTROL MANUAL
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Serial Number
May 1992
MODELS9410/14/20/24/30/50
DUAL- AND QUAD-CHANNEL
DIGITAL OSCILLOSCOPES

LeCroy
Corporate Headquarters
700 Chestnut Ridge Road
Chestnut Ridge, NY10977-6499
Tel: [phone], TWX:710-577-2832
EuropeanHeadquarters
2, rue Pr~-de-la-Fontaine
P.O. Box 341
1217 Meyrin 1/Geneva, Switzerland
Tel.: [phone], Telex: 419 058
Copyright~ May1992, LeCroy. All rights reserved, information in this
publication supersedesall earlier versions. Specifications subject to change.
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1I TABLE OF CONTENTS
General Information
Initial Inspection
Warranty
Product Assistance
Maintenance Agreements
Document Discrepancies
Service Procedure
Return Procedure
2 About Remote Control
GPIB Implementation Standard
Program Messages
Commands and Queries
Local and Remote State
Program Message Form
Command/Query Form
Response Message Form
3GPIB Operation
GPIBStructure
Interface Capabilities
Addressing
GPIBSignals
IEEE 488.1 Standard Messages
Programming GPIB Transfers
Programming Service Requests
Instrument Polls
Driving a Hard-copy Device
4 RS-232-C Operation
Introduction
RS-232-C Pin Assignments
RS-232-C Configuration
Commands Simulating GPIB Commands
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Table of Contents |
6
System Commands
Organization
Command Summary
Command Execution
Command Notation
WaveformStructure
Introduction
Logical Data Blocks of a Waveform
Inspect? Command
Waveform? Command
Waveform Command
More Control of Waveform Queries
High-speed Waveform Transfer
Status Registers
Overview of Status and Service Request Reporting
Status Byte Register (STB)
Standard Event Status Register (ESR)
Standard Event Status Enable Register (ESE)
Service Request Enable Register (SRE)
Parallel Poll Enable Register (PRE)
Internal State ChangeStatus Register (INR)
Internal State Change Enable Register (INE)
CommandError Status Register (CMR)
Device Dependent Error Status Register (DDR)
Execution Error Status Register (EXR)
User Request Status Register (URR)
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Table of Contents
Appendix A
Example1: Use of the Interactive
GPIB Program ’IBIC’
Example 2: GPIB Program for IBM PC
(High-level Function Calls)
Example 3: GPIB Program for IBM PC
(Low-level Function Calls)
Appendix B
The Waveform Template
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1
INITIAL INSPECTION
WARRANTY
PRODUCT ASSISTANCE
MAINTENANCE
AGREEMENTS
GENERAL INFORMATION
It is recommendedthat the shipment be thoroughly inspected im-
mediately upon delivery to the purchaser. All material in the
container should be checked against the enclosed Packing List.
LeCroycannot accept responsibility for shortages in comparison
with the Packing List unless notified promptly. If the shipment is
damagedin any way, please contact the Customer Service Depart-
ment or local field office immediately.
LeCroywarrants its oscilloscope products to operate within specifi-
cations under normal use for a period of two years from the date of
shipment. Spares, replacement parts and repairs are warranted for
90 days. The instrument’s firmware is thoroughly tested and
thought to be functional, but is supplied "as is" with no warranty of
any kind covering detailed performance. Products not manufac-
tured by LeCroyare covered solely by the warranty of the original
equipment manufacturer.
In exercising this warranty, LeCroywill repair or, at its option,
replace any product returned to the Customer Service Department
or an authorized service facility within the warranty period, pro-
vided that the warrantor’s examination discloses that the product
is defective due to workmanshipor materials and that the defect
has not been caused by misuse, neglect, accident or abnormal con-
ditions or operation.
The purchaser is responsible for transportation and insurance
charges for the return of products to the servicing facility. LeCroy
will return all in-warranty products with transportation prepaid.
This warranty is in lieu of all other warranties, expressed or im-
plied, including but not limited to any implied warranty of
merchantability, fitness, or adequacyfor any particular purpose or
use. LeCroyshall not be liable for any special, incidental, or con-
sequential damages, whether in contract or otherwise.
Answersto questions concerning installation, calibration, and use
of LeCroy equipment are available from the Customer Service
Department, 700 Chestnut Ridge Road, Chestnut Ridge, New
York 10977-6499, U.S.A., tel. [phone], and 2, rue
Pr6-de-la-Fontaine, 1217 Meyrin 1, Geneva, Switzerland, tel.
(41)22/719 21 11, or your local field engineering office.
LeCroyoffers a selection of customer support services. Mainte-
nance agreements provide extended warranty and allow the
customer to budget maintenance costs after the initial two year
warranty has expired. Other services such as installation, training,
enhancements and on-site repair are available through specific
Supplemental Support Agreements.

General Information
DOCUMENTATION
DISCREPANCIES
SERVICE PROCEDURE
RETURN PROCEDURE
LeCroyis committed to providing state-of-the-art instrumenta-
tion and is continually refining and improving the performance of
its products. While physical modifications can be implemented
quite rapidly, the corrected documentation frequently requires
more time to produce. Consequently, this manual maynot agree in
every detail with the accompanyingproduct. There may be small
discrepancies in the values of components for the purposes of
pulse shape, timing, offset, etc., and, occasionally, minor logic
changes. Whereany such inconsistencies exist, please be assured
that the unit is correct and incorporates the most up-to-date cir-
cuitry. In a similar waythe firmware mayundergo revision when
the instrument is serviced. Should this be the case, manual up-
dates will be madeavailable as necessary.
Products requiring maintenance should be returned to the Cus-
tomer Service Department or authorized service facility. LeCroy
will repair or replace any product under warranty at no charge.
The purchaser is only responsible for transportation charges.
For all LeCroyproducts in need of repair after the warranty pe-
riod, the customer must provide a Purchase Order Numberbefore
repairs can be initiated. Thecustomerwill be billed for parts and
labor for the repair, as well as for shipping.
To determine your nearest authorized service facility, contact the
Customer Service Department or your field office. All products
returned for repair should be identified by the modeland serial
numbersand include a description of the defect or failure, name
and phone numberof the user, and, in the case of products re-
turned to the factory, a Return Authorization Number(RAN).
The RANmay be obtained by contacting the Customer Service
Department in NewYork, tel. [phone], in Geneva, tel.
(41)22/719 21 11, or your nearest sales office.
Return shipments should be madeprepaid. LeCroywill not accept
C.O.D. or Collect Return Shipments. Air-freight is generally rec-
ommended. Wherever possible, the original shipping carton
should be used. If a substitute carton is used, it should be rigid and
be packed such that the product is surrounded with a minimumof
four inches of excelsior or similar shock-absorbing material. In
addressing the shipment, it is important that the Return Authoriza-
tion Numberbe displayed on the outside of the container to ensure
its prompt routing to the proper department within LeCroy.

2ABOUT REMOTE CONTROL
GPIB IMPLEMENTATION
STANDARD
PROGRAM MESSAGES
Twomodesof operation are available in the oscilloscope. Thein-
strument may be operated either manually, by using the
front-panel controls, or remotely by meansof an external control-
ler (which is usually a computer, but maybe a simple terminal).
This RemoteControl Manualdescribes howto control the oscillo-
scope in the remote mode. For explanations on howto manually
set front-panel controls, refer to the Operator’s Manual.
Theoscilloscope is remotely controlled via either the GPIB(Gen-
eral Purpose Interface Bus) or the RS-232-C communication
ports. Wheneverthe rear-panel GPIBaddress switches are set be-
tween 0 and 30, control is via GPIB;whenthey are at 31 or above,
control is via RS-232-C.The instrument can be fully controlled in
remote mode. The only actions which cannot be performed re-
motely are switching on the instrument or setting the remote
address.
This section introduces the basic remote control concepts which
are commonto both RS-232-Cand GPIB. It also presents a brief
description of remote control messages.
Sections 3 and 4 explain howto send program messages over the
GPIBor the RS-232-Cinterfaces, respectively. Section 5 alpha-
betically lists all the remote control commands.Section 6 is a
detailed description and tutorial of the transfer and format of
waveforms,whereas Section 7 explains the use of status bytes for
error reporting. Appendix A shows some complete programming
examples. Appendix B contains a printout of a waveform tem-
plate.
The remote commands conform to the GPIB IEEE 488.2 stan-
dard 1. This standard may be seen as an extension of the
IEEE488.1 standard which dealt mainly with electrical and me-
chanical issues. The IEEE 488.2 recommendations have also
been adopted for RS-232-C communications whenever applica-
ble.
To remotely control the oscilloscope the controller must send pro-
gram messages which conform to precise format structures. The
instrument will execute all programmessages whichare in the cor-
rect form and ignore those where errors are detected.
1. ANSI/IEEEStd. 488.2-1987, "IEEEStandard Codes, Formats, Protocols, and CommonCommands",The
Institute of Electrical andElectronics EngineersInc., 345East 47thStreet, NewYork,NY10017,USA.

About Remote Control
COMMANDS
AND QUERIES
Warningor error messagesare normally not reported by the instru-
ment, unless the controller explicitly examinesthe relevant status
register, or if the status enable registers havebeenset in such a way
that the controller can be interrupted whenan error occurs. The
status registers are explained in Section 7.
During the development of the control program it is possible to
observe all remote control transactions, including error messages,
on an external monitor connected to the RS-232-Cport. Refer to
the command "COMM_HELP"for further details.
Programmessages consist of one or several commandsor queries.
Acommanddirects the instrument to change its state, e.g. to
changeits time base or vertical sensitivity. Aqueryasks the instru-
ment about its state. Very often, the samemnemonicis used for a
commandand a query, the query being identified by a <?> after
the last character.
For example, to changethe time base to 2 msec/div, the controller
should send the following commandto the instrument
TIME DIV 2 MS
To ask the instrument about its time base, this query should be
sent
TIME DIV?
Aquery causes the instrument to send a response message. The
control program should read this message with a "read" instruc-
tion to the GPIBor RS-232-Cinterface of the controller. The
response message to the query above might be
TIME DIV 10 NS
m
The portion of the query preceding the question mark is repeated
as part of the response message. If desired, this text maybe sup-
pressed with the command "COMM_HEADER".
Depending on the state of the instrument and the computation to
be done, the controller mayhave to wait up to several seconds for
a response. Commandinterpretation does not have priority over
other oscilloscope activities. It is therefore judicious to set the con-
troller IO timeout conditions to 3 or moreseconds. In addition, it
must be rememberedthat an incorrect query message will not gen-
erate a response message.
4

LOCAL AND REMOTE
STATE
PROGRAM MESSAGE
FORM
About Remote Control 2
As a rule, remote commandsare only executed by the instrument
whenit is in the REMOTEstate, whereas queries are always ex-
ecuted. A few commandswhich don’t affect the state of the front
panel are also executed in LOCAL(refer to the beginning of Sec-
tion 5 for a list of these commands).Whenthe instrument is in
REMOTE,all front-panel controls are disabled, except the left-
hand menubuttons, the intensity controls (which can be disabled
with the command "INTENSITY") and the LOCALbutton
(which can be disabled by setting the instrument to LOCAL
LOCKOUT).For an explanation on how to set the instrument to
LOCAL,REMOTEor LOCALLOCKOUT,refer to Section 3 for
GPIB and to Section 4 for RS-232-C.
An instrument is remotely controlled with program messages
whichconsist of one or several commandsor queries, separated by
semicolons <;> and ended by a terminator:
<command/query>;......... ;<command/query> <terminator>
Upper and/or lower case characters can be used for program mes-
sages.
The instrument does not decode an incoming program message
before a terminator has been received (exception: if the program
messageis longer than the 256 byte input buffer of the instrument,
the oscilloscope starts analyzing the message whenthe buffer is
full). The commandsor queries are executed in the order in which
they are transmitted.
In GPIBmode, the following are valid terminators:
<NL> New-line character (i.e. the ASCII new-line
character, whose decimal value is 10).
<NL><EOI> New-line character with a simultaneous <EOI>
signal.
<EOI> <EOI>signal together with the last character of
the program message.
Note: The <EOI>signal is a dedicated GPIBinterface line which
can be set with a special call to the GPIBinterface driver. Refer to
the GPIB interface manufacturer’s manual and support pro-
grams.
The <NL><EOI>terminator is always used in response messages
sent by the instrument to the controller.
In RS-232-C, the terminator maybe defined by the user with the
command"COMM_RS232".The default value is <CR>, i.e. the
ASCIIcarriage return character, the decimal value of whichis 13.

About Remote Control
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Examples
COMMAND/QUERY
FORM
Example
Header
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GRID DUAL This program message consists of a
single commandwhich instructs the
instrument to display a dual grid.
Theterminator is not shownsince it
is usually automatically added by
the interface driver routine which
writes to the GPIB(or RS-232).
BWL ON; DISPLAY OFF; DATE?
This program message consists of
two commands, followed by a
query. Theyinstruct the instrument
to turn on the bandwidthlimit, turn
off the display, and then ask for the
current date. Again, the terminator
is not shown.
The general form of a commandor a query consists of a command
header <header> which is optionally followed by one or several
parameters <data> separated by commas:
<header>[?] <data> ..... <data>
The notation [?] showsthat the question markis optional (turning
the commandinto a query). The detailed listing of all commands
in Section 5 indicates which commandsmay also be queries.
There is a space between the header and the first parameter.
There are commas between parameters.
DATE15,OCT,1989,13,21,16 This commandinstructs the oscillo-
scope to set its date and time to 15
OCT 1989, 13:21:16. The com-
mand header "DATE" indicates
the action, the 6 data values specify
it in detail.
The header is the mnemonicform of the operation to be per-
formed by the oscilloscope. All commandmnemonicsare listed in
alphabetic order in Section 5.
The majority of the command/queryheaders have a long form for
optimumlegibility and a short formfor better transfer and decod-
ing speed. The two forms are fully equivalent and can be used
interchangeably. For example, the following two commandsfor
switching to the automatic trigger modeare fully equivalent:
TRIG_MODE AUTO and TRMD AUTO
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About Remote Control 2
Header path
Example
Data
Some command/query mnemonics are imposed by the IEEE
488.2 standard. They are standardized so that different instru-
ments present the same programming interface for similar
functions. All these mnemonicsbegin with an asterisk <*>, e.g.
the command"*RST" is the IEEE 488.2 imposed mnemonic for
resetting the instrument, whereas "*TST?"instructs the instru-
ment to perform an internal self-test and to report the outcome.
Somecommandsor queries apply to a sub-section of the oscillo-
scope, e.g. a single input channel or a trace on the display. In such
cases, the header must be preceded by a path namethat indicates
the channel or trace to which the commandapplies. The header
path normally consists of a 2-letter path namefollowed by a colon
<:> which immediately precedes the commandheader.
Usually one of the waveformtraces can be specified in the header
path (refer to the individual commandslisted in Section 5 for de-
tails on which values apply to a given commandheader):
C1, C2 Channels 1 and 2
C3, C4 Channels 3 and 4 (in 4-channel instruments)
MC, MD Memory C and D
FE, FF Function E and F
EA, EB Expand A and B
EX, EX10 External trigger
CI:OFST -300 MV Set the offset of Channel 1 to
-300 mV
Header paths need only be specified once. Subsequent commands
whoseheader destination is not indicated are assumedto refer to
the last defined path. For example, the following commandsare
identical:
C2:VDIV?; C2:OFST?
C2:VDIV?; OFST?
Whatis the vertical sensitivity and
the offset of channel 2?
Sameas above, without repeating
the path.
Whenevera command/queryuses additional data values, they are
expressed in terms of ASCIIcharacters. There is a single excep-
tion: the transfer of waveforms with the command/query
"WAVEFORM",where the waveform may be expressed as a se-
quence of binary data values. Refer to Section 6 for a detailed
explanation of the format of waveforms.
ASCII data can have the form of character, numeric, string or
block data.

About Remote Control
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Character data
Numeric Data
These are simple words or abbreviations for the indication of a
specific action.
BANDWIDTH LIMIT ON The data value "ON"indicates that
the bandwidth limit should be
turned on, rather than off.
In some commands, where as manyas a dozen different parame-
ters can be specified, or wherenot all parameters apply at the same
time, the format requires pairs of data values. Thefirst one names
the parameter to be modified and the second gives its value. Only
those parameter pairs to be changed need to be indicated.
HARDCOPY_SETUPDEV,HP7470A,PORT,GPIB,PSIZE,A4
Three pairs of parameters are spe-
cified. Thefirst specifies the device
as the H7470Aplotter (or compat-
ible), the second indicates the
GPIBport and the third requests
the A4format for paper size. While
the command "HARDCOPYSET-
UP" allows manymore parameters,
they are either not relevant for plot-
ters or they are left unchanged.
The numeric data type is used to enter quantitative information.
Numberscan be entered as integers, as fractions or in exponential
representation.
EA:VPOS -5 Movethe displayed trace of Expand A down-
wards by 5 divisions.
C2"OFST3.56 Set the DCoffset of Channel 2 to 3.56 V.
TDIV5.0E-6 Adjust the time base to 5 issec/div.
Note: Numeric values maybe followed by multipliers and units,
modifying the value of the numerical expression. The following
mnemonics are recognized:
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About Remote Control 2
String Data
Block Data
RESPONSE MESSAGE
FORM
EX 1E18 Exa- PE 1E15 Peta-
T 1E 12 Tera- G 1E9 Giga-
MA 1E6 Mega- K 1E3 kilo-
M1E-3 milli- U 1E-6 micro-
N 1E-9 nano- PI 1E-12 pico-
F 1E-15 femto- A 1E-18 atto-
For example, there are manyways of setting the time base of the
instrument to 5 ~tsec/div:
TDIV 5E-6
TDIV 5 US
TDIV 5000 NS
TDIV 5000E-3 US
Exponential notation, without any
suffix.
Suffix multiplier "U" for 1E-6,
with the (optional) suffix "S" for
seconds.
This data type enables the transfer of a (long) string of characters
as a single parameter. String data are formed by simply enclosing
any sequence of ASCII characters between simple or double
quotes.
MESSAGE’Connect probe to point J3’
The instrument displays this message in the Messagefield above
the grid.
These are binary data values coded in hexadecimal ASCII, i.e.
4-bit nibbles are translated into the digits 0,...9, A.... F andtrans-
mitted as ASCIIcharacters. Theyare only used for the transfer of
waveforms (command "WAVEFORM")and of the instrument
configuration (command "PANEL_SETUP")
The instrument sends a response message to the controller, as an
answer to a query. The format of such messagesis the sameas that
of program messages, i.e. individual responses in the format of
commands, separated by semicolons <;> and ended by a termina-
tor. Theycan be sent back to the instrument in the form in which
they are received, and will be accepted as valid commands. In
GPIB response messages, the <NL><EOI>terminator is always
used.
For example, if the controller sends the program message:
TIME_DIV? ;TRIG_MODENORM;C1 :COUPLING? (terminator
not shown)

About Remote Control
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the instrument might respond as follows:
TIME_DIV50 NS;C 1:COUPLINGD50 (terminator not shown)
The response message only refers to the queries, i.e.
"TRIG_MODE"is left out. If this response is sent back to the
instrument, it is a valid programmessagefor setting its time base to
50 nsec/div and the input coupling of Channel 1 to 50 ~.
Whenevera response is expected from the instrument, the control
program must instruct the GPIBor RS-232-C interface to read
from the instrument. If the controller sends another program mes-
sage without reading the response to the previous one, the
response message in the output buffer of the instrument is dis-
carded.
The instrument uses somewhatstricter rules for response messages
than for the acceptance of program messages, Whereas the con-
troller may send program messages in upper or lower case
characters, response messages are always returned in upper case.
Program messages maycontain extraneous spaces or tabs (white
space), response messages do not. Whereas program messages
maycontain a mixture of short and long command/queryheaders,
response messages always use short headers as a default. However,
the instrument can be forced with the command
"COMM_HEADER"to use long headers or no headers at all. If
the response header is omitted, the response transfer time is mini-
mized, but such a response could not be sent back to the
instrument again. In this case suffix units are also suppressedin the
response.
If the trigger slope of Channel 1 is set to negative, the query
"CI:TRSL?" could yield the following responses:
CI:TRIG_SLOPE NEG header format: long
CI:TRSL NEG header format: short
NEG header format: off
Waveforms which are obtained from the instrument using the
query "WAVEFORM?"constitute a special kind of response mes-
sage. Their exact format can be controlled with the commands
"COMMFORMAT" and "COMMORDER", as explained in
Section ~
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|3IGPIB OPERATION
GPIB STRUCTURE
This section describes howto remotely control the oscilloscope via
the GPIB.Topics discussed include interface capabilities, address-
ing, standard bus commands, and polling schemes.
The GPIBis like an ordinary computer bus, except that it inter-
connects independent devices via a cable bus whereas a computer
has its circuit cards interconnected via a backplane bus. The GPIB
carries program messages and interface messages:
¯ Program messages, often called device-dependent messages,
contain programminginstructions, measurement results, in-
strument status and waveform data. Their general form is
described in Section 2.
¯Interface messages managethe bus itself. They perform func-
tions such as initializing the bus, addressing and unaddressing
devices and setting remote and local modes.
Devices on the GPIBcan be listeners, talkers, and/or controllers.
Atalker sends program messages to one or morelisteners. Acon-
troller manages the flow of information on the bus by sending
interface messages to the devices.
Theoscilloscope can be a talker or a listener, but not a controller.
The host computer, however, must be able to act as a listener,
talker and controller. For details on howthe controller configures
the GPIBfor specific functions, refer to the GPIBinterface man-
ufacturer’s manual.
INTERFACE
CAPABILITIES Theinterface capabilities of the oscilloscope include the following
IEEE488.1 definitions:
AH1
SH1
L4
T5
SR1
RL1
DC1
DT1
PP1
CO
E2
Complete Acceptor Handshake
Complete Source Handshake
Partial Listener Function
Complete Talker Function
Complete Service Request Function
Complete Remote/Local Function
Complete Device Clear Function
Complete Device Trigger
Parallel Polling: remote configurability
No Controller Functions
Tri-state Drivers
11

GPIB Operation
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ADDRESSING
GPIB SIGNALS
Data Lines
Handshake Lines
Interface Management Lines
12
Every device on the GPIBhas an address. Whenthe thumbwheel
address switches on the rear panel of the oscilloscope are set to a
value between 0 and 30, the instrument can be controlled via
GPIB.Whenthe switches are set to above 30, the instrument can
execute talk-only operations on the GPIB, for example driving a
GPIBplotter. In this case no controller is present and the instru-
mentis directly connected to the plotter. Addresses above 30 also
enable the instrument to be controlled via the RS-232-Cport.
The instrument reads the address switches once at power on, or
whenthe RESETbutton on the rear panel is pressed. If the ad-
dress is changed during operation, the instrument must be
powered again to enable the newaddress. The value of the GPIB
address appears in the menu "Auxiliary Setups".
If the oscilloscope is addressedto talk, it will remainconfigured to
talk until a universal untalk command(UNT), its ownlisten ad-
dress (MLA),or another instrument’s talk address is received.
Similarly, if the oscilloscope is addressed to listen, it will remain
configured to listen until a universal unlisten command(UNL),
its owntalker address (MTA)is received.
Thebus system consists of 16 signal lines and 8 groundor shield
lines. The signal lines are divided into 3 groups:
¯8 data lines
¯3 handshake lines
¯5 interface managementlines
The eight data lines, usually called DI01through DI08, carry both
program and interface messages. Most of the messages use the
7-bit ASCII code, in which case DI08 is unused.
These three lines control the transfer of message bytes between
devices. Theprocess is called a three-wire interlocked handshake
and it guarantees that the messagebytes on the data lines are sent
and received without transmission error.
Thefollowing five lines managethe flow of information across the
interface.
ATN(ATteNtion): The controller drives the ATNline true when
it uses the data lines to send interface messagessuch as talk and
listen addresses or a device clear (DCL)message. WhenATN
false, the bus is in the data modefor the transfer of programmes-
sages fromtalkers to listeners.
IFC (InterFace Clear): The controller sets the IFC line true
initialize the bus.
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GPIB Operation 3
I/O Buffers
IEEE 488.1
STANDARD MESSAGES
Device Clear
REN(RemoteENable): The controller uses this line to place de-
vices in remote or local program mode.
SRQ(Service ReQuest): Any device can drive the SRQline true
to asynchronously request service from the controller. This is the
equivalent of a single interrupt line on a computer bus.
EOI (End Or Identify): This line has two purposes. The talker
uses it to markthe end of a messagestring. Thecontroller uses it to
tell devices to identify their response in a parallel poll (discussed
later in this section).
The instrument has a 256-byte input buffer and a 256-byte output
buffer. An incoming program message is not decoded before a
messageterminator has been received. However,if the input buff-
er becomes full (because the program message is longer than the
buffer), the instrument starts analyzing the message. In this case
data transmission is temporarily halted, and the controller may
generate a timeout if the limit was set too low.
The IEEE488.1 standard specifies not only the mechanical and
electrical aspects of the GPIB,but also the low-level transfer pro-
tocol, e.g. it defines howa controller addresses devices, turns
them into talkers or listeners, resets themor puts themin the re-
mote state. Such interface messages are executed with the
interface managementlines of the GPIB, usually with ATNtrue.
All of these messages (except GET)are executed immediately
upon reception and not in chronological order with normal com-
mands.
Note: In addition to the IEEE488.1 interface message standards,
the IEEE 488.2 standard specifies some standardized program
messages, i.e. commandheaders. They are identified with a lead-
ing asterisk <*> and are listed amongthe commandsin Section 5.
The commandlist in Section 5 does not contain any commandfor
clearing the input/output buffers or for setting the instrument to
the remote state. This is because such commandsare already spe-
cified as IEEE 488.1 standard messages. Refer to the GPIB
interface manualof the host controller as well as to its support
programs which should contain special calls for the execution of
these messages.
The following describes those IEEE 488.1 standard messages
which go beyond mere reconfiguration of the bus and which have
an effect on the operation of the instrument.
In response to a universal Device CLear (DCL)or a Selected De-
vice Clear message(SDC), the oscilloscope clears the input/output
13

GPIB Operation
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Group Execute Trigger
Remote ENable
Local LOckout
Go To Local
14
buffers, aborts the interpretation of the current command(if any)
and clears any pending commands.Status registers and status en-
able registers are not cleared. Although DCLhas an immediate
effect it can take several seconds to execute this commandif the
instrument is busy.
The Group Execute Trigger message (GET) causes the oscillo-
scope to armthe trigger system. It is functionally identical to the
"*TRG" command.
This interface message is executed whenthe controller holds the
RemoteENablecontrol line (REN)true and configures the instru-
ment as a listener. The REMOTELEDon the front panel lights up
to indicate that the instrument is set to the remote mode.All the
front-panel controls are disabled except the left-hand menubut-
tons, the intensity controls and the LOCALbutton. The menu
indications on the left-hand side of the screen no longer appear
since menus cannot now be operated manually. Whenever the
controller returns the RENline to false, all instruments on the bus
return to LOCAL.Individual instruments can be returned to LO-
CALwith the Go To Local message (see below).
As a rule, remote commandsare only executed when the instru-
ment is in the remote state, whereas queries are always executed.
Local front-panel control maybe regained by pressing the LO-
CALpush button, unless the instrument was placed in the Local
LOckout (LLO) mode.
The Local LOckout command(LLO) causes the LOCALbutton
on the front panel of the oscilloscope to be disabled. The LLO
commandcan be sent in local or remote mode but only becomes
effective once the instrument has been set to the remote mode.
The Go To Local message (GTL) causes the instrument to return
to the local mode.All front-panel controls becomeactive and the
menuson the left-hand side of the screen reappear. Thereafter,
wheneverthe instrument is addressed as a listener it will be imme-
diately set to the remote state again.
Note that a GTLmessagedoes not clear the local lockout if it was
set. Thus, wheneverthe instrument returns to the remote state the
local lockout modewould immediately be effective again.
A commandstring should not be immediately followed by a GTL
message. Since GTLis executed at once, the instrument mayal-
ready be returned to the local state before the commandsin the
input buffer are interpreted. Therefore, the instrument mayrefuse
to execute them if they require the instrument to be in REMOTE.
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