LeCroy 7200 User Manual
1-1
GPIB Signals and Lines
,!*
GPIB Remote Control
The General Purpose Interface Bus (GPIB) te originally based on the IEEE Standard 488, 1976 (and later revised
IEEE 488.1,1987).
The GPIB can interconnect many instruments to allow communication with one another over
shared cables. The GPIB uses a bit-parallel, byte-sedal format. The 7200A can achieve a
maximum transmission rate of 400 kBytes per second.
A device connected to the GPIB is either a talker, listener, or controller. Although some devices can change roles, a device can perform just one role at a time.
Talker Places messages or data on the network for transmission to
other devices. Only one device on the network can be ithe talker.
Listener
Receives data or commands over the network. Several listeners
may be active at one time.
ControIIer,,~;
ei: ¯
Governs the operation of the network. A controller, usually a
computer, normally sends program messages to devices and receives response messages from them. One controller task is to
decide which device is the talker and which is a listener(s). The
controller may assign itself to be the talker at one time, and a
listener at other times. If devices on the network never change
their roles, a controller is not required.
The Communications Screen allows you to select GPIB as the Remote Control port and set
the GPIB address for the 7200A. The Hardcopy screen allows you to select GPIB as the
hardcopy port for printers and plotters. If GPIB is the selected port for hardcopy, no controller is needed and all other devices on the bus must be in =Listen Only" mode.
GPIB Signals and Lines
The GPIB has 16 signal lines and eight ground return lines. Eight of the 16 signal lines form
a bi-directional data bus which transfers data and commands. The remaining eight signal
lines control the bus operation. Three lines are for handshake signals which synchronize
data transmission. The remaining five are management lines which control the flow of information across the interface.
1-2
t
GPIB Host and Hardcopy Operation
Setting the GPIB Address
The GPIB address is set in the Communications screen. From the Main Screen, press the
Configure System softkey to display the Configure System setup screen. Then press the
Communication Setup softkey to display the Communications Setup screen. Move the box
onto the =Remote Control from" field and select GPIB. Then move the box onto the =GPIB
Address" field and select an address from 0 to 30.
GPIB Host and Hardcopy Operation
The 7200A can communicate across GPIB as a talker or a listener with a remote host controller to receive remote commands/queries and send responses. For this talker/listener remote control operation, the 7200A conforms to the guidelines specified by IEEE 488.2. The
hardcopy output can also communicate across GPIB in one of two ways. First, if the hard-
copy port is the same as the remote control port, then a remote hardcopy command sends
the output to the remote host as a query response. Second, if the hardcopy port is different
from the remote control port or and the local hardcopy key is pressed, then the 7200A enters
Talk Only mode and does not expect any controller present on the bus~ ~ ::
Remote Control Operation over GPIB ....
Talk/Listen The 7200A enters this mode when the =Remote Control from"
field in the Communications Setup screen is set to GPIB. In this
mode, the 7200A can both receive commands and setups from
the remote host computer and send data and measurement resuits.
~ :
~ .~ ¯
"
Hardcopy Operation over GPIB
Talk Only To output hardcopy data over GPIB, the =Hardcopy Port" field in
the Hardcopy screen must be set to GPIB. Setting the Hardcopy
Port has no effect on the selected port until the hardcopy is initiated. If the Hardcopy Port is GPIB, then pressing the local Hardcopy key will force the 7200A to enter Talk Only mode. Also, if
the Hardcopy Port is GPIB and the Remote Control port is RS-
232-C, then initiating a hardcopy remotely from RS-232-C will
also force the 7200A to enter Talk Only mode. Talk Only is a spe-
cial GPIB mode where there is no controller allowed on the bus;
the 7200A is the only talker and all connected devices must be
listeners (ie., printers/plotters must be in Listen Only
mode). However, if both the hardcopy port and =Remote Control
from" field are set to GPIB, then pressing the local Hardcopy key
1-3
GPIB Host and Hardcopy Operation
just sets the User Request (URQ) bit in the Standard Event
Status (*ESR) register, the 7200A cannot enter Talk Only mode
since this may disrupt the conb’oller. Instead, the controller may
query the *ESR register and if the URQ bit is set, the controller
may halt bus activity and synchronously initiate a remote Hard-
copy as describes next.
Talk/Listen
When both the Hardcopy Port and the Remote Control port are
set to GPIB, then sending the remote command "HARDCOPY"
or "HCPY" over GPIB from the host computer will cause the
7200A to send the hardcopy output to the host computer as a re-
sponse message. In this mode, the 7200A will wait to be addressed to talk before sending the hardcopy data. The host
computer then has three options in generating the hardcopy:
1) The host computer may read the data into Internal memory
and then send the data to a printer/plotter. This is exactly the
same as reading a query response.
2) The host computer may send the =HARDCOPY" remote command and then address the printer/plotter to listen and the
7200A to talk and read the data from the 7200A. As the data is
read into the computer’s internal memory, it is also printed/plot-
ted to the printer/plotter which is a Listener.
3) The host computer may send the "HARDCOPY" remote com-
mand and then address the printer/plotter to listen, the 7200A to
talk, and the controller to go into stand-by mode waiting for EOI.
Altematively, the Data Processing Status Register (DPR) could
be programmed to issue an SRQ when hardcopy is complete so
that the host computer can perform other tasks while the hardcopy is performed.
1.4
GPIB Host and Hardcopy Operation
GPIB
GPIB
RS232
RS2.32
Centronics
Floppy
GPIB
RS232
RS232
GPIB
GPIB/
RS2.32
RS232/
GPIB
Sets the URQ bit in the
*ESR register.
Hardcopy data output in
Talk-Only mode. Address
the device at address 30
to listen before sending
data.
Sets the URQ bit in the
*ESR register.
Hardcopy data is output
immediately.
Hardcopy data is output
immediately.
Hardcopy data is written
to a floppy disk
immediately.
Hardcopy data output
when the controller
addresses the 7200A to
talk.
Hardcopy data output in
Talk-Only mode. Address
the device at address 30
to listen before sending
data.
Hardcopy data output
when controller asserts
CTS (Hardwire mode)
until receipt of XOFF.
Hardcopy data is output
immediately.
Hardcopy data is output
immediately.
Hardcopy data is written
to a floppy disk
immediately.
1=5
GPIB Device Interconnections
GPIB Device Interconnections
The devices on the GPIB network may be connected in any combination of star or linear ar-
rangements (Figure 1.1 ). Standard IEEE 488.2 cables must be used to connect all the de-
vices and total length must not exceed 20 meters. The devices must conform to these rules:
¯ At least half the devices on the network must be turned on.
¯ One network can connect no more than 15 devices (including the controller).
One device must be connected for every two meters of cable, assuming one
¯
device presents one standard device load. The 7200A’s GPIB connector is
located on its rear panel.
Each device must have a unique bus address.
¯
1-6
OL=VtC;E A
DL=VlCE D
DEVICE B
DEVICE B
DEVICE C
I I EC
STAR CONFIGURATION LINEAR CONFIGURATION
Figure 1.1 : Examples of GPIB Network Arrangements
RS-232-C Remote Control
The 7200A interface is defined by the following GPIB function codes:
For a description of these functions and their subsets, see IEEE Standard 488.1, Section 2.2 through 2.12.5. The
IEEE Standard is published by the Institute of Electrical and Electronics Engineers, Inc., 345 East 47th Street, New
York, New York 10017.
INTERFACE FUNCTION
Controller (CO)
Source Handshake (SH1)
Acceptor Handshake (AH1)
Talker (T6)
Listener (L4)
Service Request (SR1)
Device Trigger (DT1)
Device Clear (DC1)
Parallel Poll (PP0)
Remote Local (RL1)
Electrical Interface (E2.)
*Unaddress refers to the action taken when the interface switches its
function. This action effectively clears the current function before the
next function is selected.
Table 1.1: 7200 IEEE-488 Function Codes
RS-232-C Remote Control
No controller capability.
Complete source handshake capability.
Complete acceptor handshake capability
Basic talker with serial poll capability and
unaddress* if MLA (My Listen Address).
Basic listener with unaddress if MTA (My
Talk Address).
Complete serial poll capability.
Capable of responding to device trigger.
Responds to device clear (universal or
selective).
No parallel poll capability
Complete remote/local capability
SRQ, NRFD, and NDAC are tri-state lines
The 7200A can also be operated from a computer or terminal via its RS-232-C port. RS-232C uses serial transmission and complies with the Electronic Industries Association’s RS-232-
C standard. (The equivalent international standard is ISO V24 which is generally compatible
with the RS-232-C version.)
Unlike the GPIB where many devices can be interconnected, the RS-232-C connects just
two devices. Only three communication lines are necessary to establish the interface: trans-
mired data, received data, and logic ground. However, the additional lines, RTS (request to
send) and CTS (clear to send), permit transfer of data only after confirming that the receiving
1-7
RS-232-C Configuration
device is capable of accepting more data. That is, the sender sends an RTS and waits for a
CTS from the receiver before sending data. This protocol guarantees that data does not over-
run the receiver’s buffer.
RS-232-C offers compatability with most computers. It uses a bit-serial data format with a
maximum transmission rate of 19,200 bits per second, much less than that of GPIB.
Each data word is transmitted as a separate packet with its own start and stop markers, or
bits. The RS-232-C standard defines the electrical characteristics of these bits and the composition of each packet. Their composition and transmission rate must be the same for both
the device and the 7200A. The Communications Setup screen is used to select transmission
rate, error checking (parity), and number of stop bits. In order to establish communications,
additional serial transmission characteristics may be set remotely using the COMM_RS232
remote command. See Section 5: Communication Commands for a description of this command.
RS-232-C Configuration
Setup the Serial Port
The 7200A contains a 9-pin, male RS-232-C connector for serial communication with a
printer, terminal, or computer. To connect an RS-232-C line to the 7200A, use a female DB9-
D connector. If the computer has a DB25-D connector, use a DB9-D to DB25-D cable adapter. The optional CTS and RTS handshaking guarantees that data passed between a remote
computer and the 7200A will not overrun the 7200A or the computer’s RS-232-C buffer.
Select the desired settings for the interface using the Communications Setup screen:
1. From the Main Screen, press the Configure System softkey to display the Configure
System setup screen.
2. Then press the Communication Setup softkey to display the Communications Setup
screen.
RS-232-C Host lnterconnection
Although the RS-232-C standard defines signal lines and electrical characteristics, it does
not define mechanical characteristics. The 7200A RS-232-C output port is configured as an
RS-232-C Data Terminal Equipment so that data is sent from pin 2 and received on pin 3.
For remote operation, the RS-232-C port must be connected to a computer terminal.
The following diagrams are used for various host drivers.
1-8
RS-232-C Configuration
"Data Communication Equipment"
(7200A)
"Data Terminal Equipment"
Figure 1.2: RS-232-C Connection to an IBM-PC Host
DB9 to DB25 Wiring
This wiring configuration is used for IBM-PCs and compatibles with DB25-D connectors
configured as Data Terminal Equipment¯ Note that for XON-XOFF communication protocol,
only pins 2, 3, and 5 on the DB9-D connector are needed¯ Also, commercially available DB9to-DB25 adapter cables for the IBM-PC swap pins 2 and 3 and pins 7 and 8.
7200A
(DB9, DTE)
Pin 2
Pin 3
Pin 5
If Hardwaire handshaking is used (see "Communications Setup,
page 3-119"), the following connections must also be satisfied.
Pin 7
Pin 8
Computer
(DB25, DTE)
Tx Pin 2
Rx
Gnd
CTS
RTS Pin 4
Pin 3
Pin 7
Pin 5
1-9
RS-232-C Configuration
DB9 to DB9 Wiring
For IBM PC-AT types with DB9-D connectors configured as Data Terminal Equipment.
7200A Computer
(DE9, DTE) (DB9, DTE)
Pin 2
Pin 3 Pin 3
Pin 5
If Hardwaire handshaking is used (see "Communications Setup,
page 3-131"), the following connections must also be satisfied.
Pin 7
Pin 8 --~,
\/
Tx
Gnd
CTS
Rx
Pin 2
Pin 7
Pin 5
Pin 4
DTE to DCE Wiring
For non-IBM types with DB9-D connectors configured as Data Communications Equipment.
7200A Computer
(DB9, DTE) (DBg, DCE)
Pin 2
Pin 3 Pin 3
Tx
Rx
Pin 2
1-10
Pin 5
If Hardwaire handshaking is used (see "Communications Setup,
page 3-131"), the following connections must also be satisfied.
Pin 7
Pin 8 Pin 8
Gnd
CTS Pin 7
Pin 7
RS-232-C Configuration
RS-232-C Interconnections for Hardcopy
When connecting an RS-232-C serial printer/plotter to the 7200A, the printer/plotter configu-
ration must match the 7200A RS-232-C port settings. To modify settings, use the Communi-
cations Setup screen.
RS-232-C Connection
=Data Terminal Equipment"
=Data Communication Equipment"
(7200A)
Figure 1.3: RS-232-C Connection to an RS-232-C
Serial Plotter
DB9 to DB25 Wiring
NOTE: The 7200A RS-232-C interface is a DB9-D connector. Use
an adapter cable to connect to an RS-232-C DB25-D connector.
Pin2
Plot I
Pin4
Pin8
Pin8
PIn 7
~n2
~n8
~n7
Pin4.
Pin5
Pin6
Pin 20
Pin 8
1-11
RS-232-C Host Operation
Parallel-Centronics Wiring
The 7200A uses a standard DB25-D female connector as the Centronics parallel output port.
An adaptor cable is required to adapt the 7200A DB25-D connector to the standard 36-pin
bail lock connector used on most Centronics printers.
7200A ~
Printer
Figure 1.4: Output to Centronics type Printer/Plotter
RS-232-C Host Operation
The 7200A may be controlled by a Remote Host computer in a similar manner as in GPIB. It
is able to accept commands, strings, and arbitrary block data and send back responses to
queries. However, RS-232-C communications is limited to the transfer of ASCII characters
in the range 1 to 127. Also, any character whose value is below a <space> (ASCII 32) can
not be used as part of a valid command or query but may be used as a valid <PROGRAM
MESSAGE TERMINATOR>. The exception to this rule is the <ESCAPE> character (ASCII
27). When <ESC> is sent to the 7200A, the very next character sent is interpreted to have
special meaning.
1-12
The valid Escape sequences are as follows:
RS-232-C Host Operation
Command
<ESC>(
<ESC>)
<ESC>[
<ESC>]
<ESC>C
<ESC>R
<ESC>L
<ESC>F
<ESC>T
All <ESC> commands are immediately executed upon being parsed. Their intent is to simulate GPIB commands over the serial port.
When the 7200A receives ASCII block data in excess of its input buffer size it will send
XOFF (ASCII 19) to hold up the transfer of data from the Remote Host until it has processed
the current buffer. Also, if the handshake mode is HARDWlRE, it will de-assert CTS (Clear
To Send). When the 7200A is ready for more data, it will send XON (ASCII 17) and assert
CTS.
Descriptiorl
Selects HARDWIRE handshake mode
Selects XON-XOFF handshake mode
Selects Echo off (half-duplex mode)
Selects Echo on (full-duplex mode)
Sends a DCL (device clear) command
Sends a REN (remote enable) command
Sends an LCL (local enable) command
Sends an LLO (local lockout) command
Sends a GET (group execute trigger) command
Table 1.2: Valid Escape Sequences
For a complete description of setting the configurtation of the RS-232-C port for Remote
Host communications, see the COM_RS232 remote command in Section 5 (Communication
Commands).
1-13
Section 2: Command S ntax
The following segments describe the rules and syntax for controlling the 7200A from a remote computer over either GPIB or RS-232-C. Any differences between the ports are noted.
Message Types
Commands
Responses
Waveforms
Status
With few exceptions, all commands, responses, and status messages are encoded accord-
ing to the American Standard Code for Information Interchange (ASCII) and are strings
printable characters. Upper and lower case characters are interchangeable.
Commands have two categories: action and query.
An action command causes the 7200A to make an assignment
or perform a function. For example, it might cause the 7200A to
calibrate all the plug-ins, or an assignment may result in a new
front panel setting, a communication parameter receiving a new
value, or the date being set.
Commands that request results are called queries. They ask the
7200A to return waveform data, settings, or measurements.
These are replies sent from the 7200A in response to query com-
mands.
Waveform data is a special form of response. It may be output in
binary or hexadecimal formatted blocks. These formats are more
compact than that used for response messages, so a large number of data points can be transferred in less time.
A status message indicates the 7200A’s current internal state.
2-1
Command Processing
Message Direction
As shown in Figure 2.1, the controller sends commands to the
7200A, and the 7200A sends waveforms, responses, and status
messages back to the controller.
Controller
Action and Query
Commands
Waveforms
Responses
Status
Figure 2.1: Message Directions
7200A
Command Processing
Commands are not processed until the 7200A receives an <end>, or, in the case of waveform input, when the 7200A input buffer is full (i.e., normally, no action is taken on any part
of a command message until the entire message is received or the message size exceeds
the input buffer size).
Command Processing Order
Valid commands are processed in the order they are received.
Some remote commands cannot be performed immediately. For example, it is not possible
to read channels that are armed and waiting for a trigger, since the memories associated
with these channels are continuously being written. If the 7200A receives a command it cannot perform immediately (another example is the STORE of a channel), it defers executing
the command until the needed waveform is acquired.
2-2
IEEE-488 Standard Messages
Command Errors
Before attempting to execute a command or query, the 7200A confirms that all the required
parts of the command are provided, and that all the arguments are within required ranges.
If an error is generated, the 7200A will set the appropriate status and, if enabled, report it to
the host computer. The host can then interrogate the status byte(s) to determine the nature
of the error. Refer to Section 4 for details on status bytes.
NOTE: Commands preceding and following an error in
multi-command messages are still executed. This provides
consistent operation whether commands are sent one at a time or
several per message.
Output from the 7200A
When the 7200A generates a response to a query, the controller should read it before sending a second query. If the controller sends a second query before reading the response to
the first one, the 7200A interprets this as an Interrupted Action and performs the following:
1. Upon receiving the <end> of the second query, the 7200A flushes its output buffer of all responses to previous queries.
2. The 7200A sets a Query Error bit, and
3. The 7200A fills the output buffer with the response to the second query.
IEEE-488 Standard Messages
This section explains how the 7200A reacts to the Standard 488.2 messages.
NOTE: This section pertains to GPIB only
Serial Poll Function The 7200A implements a full Serial Poll Interface Function:
1. It can assert the SRQ (Service Request) control line.
2. It will respond with the current serial poll byte or STB when
addressed to Talk and after the Serial Poll Enable interface
message is received.
3. After transmitting its status message, the 7200A stops assert-
ing the SRQ line and clears its internal status byte.
Receiving the Trigger
Message
The 7200A responds to the Trigger message [Group Execute
Trigger (GET) or the *TRG command] by arming all plug-ins.
The trigger signal, also available on the rear panel, can be used
2-3
IEEE-488 Standard Messages
for external hardware or event synchronization to internal 7200A
operations. It is executed after all previously received commands
have been processed.
Interface Clear
Device Clear (Sdective
or Universal)
Go to Local, Go to Remote,
Go to Remote with
Lockout Local
The Interface Clear message (asserting IFC line) is an asynchronous control line that causes all bus activity to halt. When the
7200A receives the IFC message, it becomes unaddressed,
stops talking or listening, and will not participate in future bus
transactions until readdressed to talk or listen.
The 7200A will respond to a Selective Device Clear or a Univer-
sal Device Clear interface message. The former requires that the
7200A first be addressed to listen, followed by the Selective Device Clear message. The latter does not require that the instru-
ment be previously addressed to listen. Device Clear causes the
input buffer, the output queue, and the message available
(MAV) status bit to be cleared.
The 7200A can operate in Local or Remote mode. In Local
mode, all front panel controls are operational and commands
from the host computer will also be processed. In Remote mode,
the 7200A operates under computer control and no front panel
controls are operational except the Local softkey (if enabled).
(The 7200A always powers on in Local mode.)
NOTE: The 7200A processes all messages regardless of being
in Remote or Local modes.
The 7200A switches to Remote mode (with Local softkey enabled) when the 7200A receives the command "REM", or a com-
mand is sent with the REN line asserted. All instrument settings
remain unchanged during local-to-remote transitions. The lower
left part of the 7200A screen indicates that Remote mode is enabled and the Local softkey appears. No other front panel controis operate.
2.4
If the 7200A is under remote control and the Local softkey is
pressed, the instrument interrupts program control and returns to
local control. Data and/or settings can now be changed locally.
CAUTION: To prevent a transition back to local mode the 7200A
can be placed in a Local Lockout state using the "LLOK" command. in Local Lockout state, all front panel keys and knobs are
IEEE-488 Standard Messages
disabled. Once Remote with Local Lockout is set, it can only be
cleared when the 7200,4 is put into Local mode by sending the
=L OC" command or readdressing the 7200A with REN deas-
serted.
Message Syntax
Messages consist of one or more data bytes which are sent over the bus.
All messages sent to and received from the 7200A are formed of English words except for
waveform transfers. Abbreviations, typically two to four characters, are also defined to
achieve higher throughput. Lower or upper case alphabetic characters are interchangeable.
NOTE: Any message received by the 7200A must conform to IEEE-
488.2 syntactic requirements. (If a violation is detected, the 7200A
will generate an error which indicates an invalid command.) The
syntax for each type of message is described below.
Action Command Syntax
Commands are sent to the 7200A to initiate various actions. They contain Headers, sometimes an Argument(s), and a Terminator:
Header Identifies what action to take; e,g., set the date, stop acquisition.
Ar~nt(s)
Terminator
Qualifies or supplements the header. The argument acts as a parameter(s) or data to the header. It is included in the command
only if a header is defined to require an argument(s). For example, an argument indicates what date to set.
Indicates the end of the command message. GPIB and
RS-232-C have different message terminators. In this manual,
the command message terminator is represented by <end>.
2-5
IEEE-488 Standard Messages
r
Space
mnemonic ~j_
I
’ Long Form
mnemonic
, Short Form
I
HEADER
I
Figure 2.3: Action Command Syntax
Unless specifically noted, white spaces (ASCII 32 decimal) between the parts of a command
do not affect its processing. Upper and lower case characters are interchangeable. The general format of a command follows:
Command Header
PREFIX I
Plug.in channel
I
2-6
Figure 2.2: Command Header
Command Arguments
IEEE-488 Standard Messages
--~ Numeric
~
’ ’ String ~
Figure 2.4: Command Arguments
Query Syntax
The Syntax of a Query is very similar to that of an Action command. A Query command adds
a question mark (=?") immediately after the last character of the header. For example, to find
the current value for the offset on channel 2 of plugin B, send: B2:OFFSET?.
NOTE:Many action commands have a corresponding query command which may have
arguments.
Figure 2.5: Query Syntax
2,-7
IEEE-488 Standard Messages
Multiple Commands
A message containing more than one command before the terminator is called a compound,
or multiple command message.
Sending a multiple command increases throughput. Each command (header and any arguments) is separated from the following one by a semicolon (";"). Space(s) on either side
the semicolon do not affect processing. Upper and lower case characters are interchangeable.
ACTION 1
j
COMMAND -
QUERY 1 "
COMMAND
Figure 2.6: Multiple Commands
A multiple command can include Action and Query commands. For example, one multiple
command can perform auto setup, request the current time and date being used, and execute a trigger command as follows:
ASET; DATE? ; *TRG <end>
2-8
IEEE-488 Standard Messages
Command Header
A command header defines the action to perform. The header begins with a letter and can
be followed by any combination of up to 15 letters, numbers, and underscores. Any com-
mand with more than four characters has a short form. (Long and Short form headers can be
intermixed.) Using the short form (four or less characters) increases throughput. The long
form, however, makes understanding program code easier. For example, to set the timebase
remotely, either TIME DIV or TDIV can be sent.
Command headers comprise three broad categories according to their syntactic make-up:
¯
Directed Header,
¯ System Header, and
¯ Standard Header.
Directed Header
This type of header directs an action at an object. The object can be either a plug-in, chan-
nel, trigger source, or trace. The prefix identifies the object being acted upon. It is followed
by a colon (=:") and the header which indicates the action performed.
prefix:header
Only one prefix is permitted per header.
NOTE: If a command is defined as having a prefix, the prefix must always be specified.
The types of prefixes are:
Mug.in The plug-in is identified by location. The mainframe plug-in slot
nearest the display is slot A. Slot B is to the right of A.
Use the plug-in prefix on/ywhen a command operates on the
plug-in controls, such as when setting the timebase. To set the
timebase to 5 msec per division for the plug-in in slot A, for example, use the command:
A:TIME_DIV 5ms
2-9
IEEE-488 Standard Messages
Channel
Source
The input channel is identified by its location in the plug-in. The
uppermost left BNC connector in plug-in A is labeled AI. The
next lower connector is A2, and so on. To modify all channels,
do not specify a specific channel.
Use the channel prefix only for commands which affect vertical
amplifiers, such as when setting the vertical sensitivity. To set
the vertical sensitivity to 5 mV per division for plug-in A, channel
1, for example, use the command:
A1 :VOLT_DIV 5mV
To set all of the plug-in’s channel settings to be the same, use
the plug-in prefix with no channel designation. For example, to
set offset to 10 mV for all channels, use the command:
A:OFST 10 mV
Since a rigger command can specify settings for each trigger
source, it must be specified as a prefix. The prefix symbols are
either:
An input channel as previously defined;
Plug-in and =EX" for the external trigger signal;
Plug-in and =EX10" for the external tdgger signal divided by
ten; or
Plug-in and =LINE" for triggering on the power line frequency.
2-10
Trace
To set the trigger level to 5 mV per division for the external trigger signal divided by ten, for example, use the command:
AEX10:TRIG_LEVEL 5mV
Traces 1 through 8, indicated as T1 through T8, define the processing and display characteristics of traces. For example, to
query the horizontal position of trace 7 use the command
T7:HOR_POSITION?
IEEE-488 Standard Messages
System Header
This type of header indicates an action that affects general oscilloscope operation; that is, an
operation not necessarily restricted to a particular plug-in, channel, or trace. Examples are
changing the grid selection and cursor type. The System Header format disallows a prefix.
For example, to turn on local display processing, use the command:
DISPLAY_ON
Standard Header
This type of header indicates a command that is explicitly required by the IEEE-4882 standard. These commands have the same format as the System Header, except an asterisk ("*")
immediately precedes the first letter of the command. For example, the *RST command initiates a device reset, *IDN? asks the device for its identification.
Command Argument(s)
A command argument(s) qualifies or supplements the header. It is included in the command
only if a command is defined to require an argument(s). For example, an argument indicates
what value to set for volts per division.
Most commands require one or more arguments to describe a desired action in detail (see
Figure 2.4). The first argument is separated from the header by one or more spaces. Argu-
ments are separated from each other by commas.
The possible types or arguments are:
Decimal Numeric Any number in numeric repesentations NR1, NR2, or NR3 as de-
fined by ANSI X3.42-1975. These refer to integers (e.g., -45),
floating point (e.g., 3.1443), or exponential values (e.g.,
3.1459E+00), respectively.
The ASCII characters "E" or "e" are used to delimit the mantissa
from the exponent in exponential arguments. Spaces are allowed between the exponential delimiter and the digits (0
through 9), but are not allowed between digits, or between the
decimal point (.) and the digits.
Numeric values with fractional parts must be expressed as a
floating point or an exponental value. For example, 3.14159 and
3.14159E+00 are both acceptable standard formats.
2-11
IEEE-488 Standard Messages
The allowable range depends on the command. If a numeric is
sent to the 7200A and has a precision greater than allowed, the
7200A will truncate, process the result, and generate a warning.
If a numeric not included in the specified set is sent, a valid numedc closest to that sent is used. For example, vertical position
must be specified with a value that is a multiple of 0.02. If 68.01
were sent, 68.00 is used.
Suffixes can replace exponential notation. For example, these
commands are equivalent:
TIME_DIV 5.00E-6
TIME_DIV 5.00 US
Valid suffixes are listed in the following table:
Allowed<Suffix Mult.>Mnemonics
Definition Mnemonics
1E18
EX
1E15 PE
1E12 T
1 E9 G
1 E6 MA
1E3 K
1E-3 M
1E-6
U
1E-9 N
1E-12
P
1E-15 F
1E-18 A
NOTE: Only engineering unit multipliers
are allowed.
Table t~cen from ANSI/tEEE SId 488,2-1987
Table 2.1: Valid Suffix Mnemonics
2-12
IEEE-488 Standard Messages
Non-Decimal
Numeric
String
Numbers can also be used in bases other than base 10. For example, each bit in a status byte may be understood better if the
byte is specified in hexadecimal or binary.
Precede non-decimal arguments with a pound sign ("#") followed by an "H" for hexadecimal, "Q" for octal, and "B" for bi-
nary. Note that numbers are treated as unsigned with an implicit
radix point. For example, #HFF and #B11111111 are both 255.
Some commands require or allow String arguments such as
"ON" or "OFF". These arguments contain 7-bit ASCII alphanu-
meric characters. A string begins with an alpha character which
may be followed by alphanumeric characters A through Z, a
through z, 0 through 9, and =._". Carriage return or line feeds are
not valid characters. Note that the oscilloscope treats upper and
lower case characters identically.
Each command definition specifies the maximum number of
characters for its string argument(s).
Quoted strings are delimited by either an apostrophe (’) or a quo-
tation mark (=). The 7200A returns quoted strings with quotation
marks. The same type of delimiter that opens a quoted string
must close it. Strings within strings are allowed as long as each
string has the same opening and closing delimiters.
Waveform Data
A quoted stdng may not be terminated with an <end> character.
For example, "test <end> is an invalid string.
The WAVEFORM command lets you send or read a complete
waveform. The waveform usually contains a very large amount
of data. Due to its length, a special formatting convention is used
to transfer the large data blocks. See page 2-17 "Waveform
Data Syntax" for an explanation of this format.
2-13
IEEE-488 Standard Messages
Keywords
Some commands have several arguments. For example, the command for configuring a
hardcopy device can have up to ten arguments that set such characteristics as plotter speed
and paper size. Rather than listing every argument when only a few need changing, the argu-
ment specified is identified by a =keyword".
A keyword is a character argument that must be followed by a comma, and then an associated value for the characteristic being set. The value may be one of the four types of arguments previously described.
Arguments not specified remain unaffected.
For example, the INTENSITY command is used to program the brightness of the traces and
grids independently. To set the grid’s intensity to half scale, send: INTENSITY GRID,,50. The
trace intensity remains unchanged.
For commands with several keywords, the order of the keyword-value pairs does not matter.
NOTE: A multi-argument command that does not use keywords
must have all its arguments listed, and ordered in the same sequence as shown in the command definition.
An example of a command with no keywords is the date command, which requires specifica-
tion of the day followed by the month, etc.
When querying most keyword commands, you can give the keyword(s) as an argument. For
example, CRST? HABS, VABS returns only the absolute horizontal and vertical cursor posi-
tions. If no argument is specified, all values are returned.
Command Terminators
Commands sent one at a time must end with a terminator. In this manual, terminators are indicated by <end>. Alternatively, multiple commands can be sent together by terminating
each command with a semicolon and terminating the entire multiple command message with
<end>.
GPIB Terminators
The only valid GPIB terminator is Eel (End or Identify) asserted with the last character sent.
This is necessary because of the possibility of binary data transmission into the 7200A
would make termination on a line feed alone impossible.
NOTE: The 7200A always terminates its response messages with a
line feed character with EOI asserted.
2-14
Response Syntax
RS-232-C Terminators
The COMM_RS232 command is used to define the <end> for command messages, and
separately for response messages.
The keyword El defines the <end> of command messages as a number from 1 through 127.
The default value is carriage return (decimal 13). If another value is selected, it must not
used elsewhere in the command argument; otherwise, the 7200A will prematurely terminate
the command.
The keyword EO defines the end of messages transmitted by the 7200A. The initial value is
CR LF (carriage return, then line feed).
For example, Arbitrary Block Program Data suitable for waveform transfers is sent as ASCII
alphanumeric characters between the range 0 through 9 and A through F. Therefore, select
a number that does not have a value corresponding to the ASCII decimal values of these al-
phanumeric characters.
Response Syntax
Query commands sent to the 7200A result in information being returned. The packet of re-
turned information is called a response message. This message typically contains measure-
ment results, settings, or status information. If multiple queries are sent in the same
command, the responses will be returned in one multi-response message with the individual
responses separated by semicolons (";").
The computer should completely read any responses from the 7200A before sending new
queries. If the computer sends a query command, starts reading the response, and issues
another command before completely reading the results of the first query, the 7200A interprets this as an interrupted action, sets the query error status bit, clears the output
queue,and sends the second response.
Responses conform to a general format, and with few exceptions are ASCII strings of print-
able characters. Generally, the syntax of any response is as follows:
2-15
Response Syntax
where
<header>
<argument data>
HEADER
Figure 2.7: Response Syntax
The syntax of a response header is the same as for a command
header (see page 2-9). Prefixes are supplied when applicable.
The header can be retumed in either short, long, or no header
(OFF) format as specified by the command COMM_HEADER
(see page 5-21). Short format produces an adequate response
for most circumstances. The long format yields the header in full
English format for increased legibility. The OFF format achieves
the fastest response time and requires little or no parsing.
This part contains the information requested by the query com-
mand. It is separated from the header by one space. The argument data can be any of the types described in the Command
Arguments section, p. 2-11.
one
space
Arguments
2-16
<end>
For GPIB, the <end> of a single or a multi-response message is
always a line feed sent with EOI asserted.
For RS-232-C, <end> is the current setting of the EO argument
of the COMM_RS232 command which is defined as a string.
The default string is a CR (carriage return) followed by a LF (line
feed). These are decimal 13 followed by decimal 10.
If the <end> string is contained within the response message,
the computer may prematurely terminate the response from the
7200A. Programming <end> is provided for flexible response for-
mats but must be used with caution.
Waveform Data Syntax
If COMM_HEADER SHORT was sent before the following multi-response message:
T1 :HOR_POSlTION?; *STB?; T1 :VERT_POSrrlON?<end>
The response would be:
T1 :HPOS 1.0,1; *STB 48; VPOS 1.0<end>
Waveform Data Syntax
Waveform data is a specially formatted argument used to transfer large amounts of binary or
hexadecimal data. The WAVEFORM command uses this argument to send data to, or to
read data from the 7200A.
The 7200A supports three block data formats:
¯ Definite length arbitrary block data,
¯ Indefinite length arbitrary block data, and
¯ "OFF".
The COMM_FORMAT command (see page 5-19) is used to select the desired format.
Waveform Data transfers are used by the 7200A to send waveforms to a host controller. The
waveform query will be used in this section to describe the waveform data response format.
The WF? waveform query may optionally be followed by ALL, DESC, TEXT, DAT1, and
DAT2 to query specific parts of the waveform. If nothing follows the WF?, then ALL is as-
sumed.
Data Element Format
Each waveform point is called a data element. Using two commands, COMM_FORMAT and
COMM_ORDER, the 7200A supports several methods of forming data elements. You can
specify:
¯ the size or the width of the data element (i.e., the number of bytes),
¯ how it is encoded (i.e., binary or hexadecimal) and
¯ the arrangement of bytes for multi-byte words.
2-17
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