OPERATOR MANUAL FOR
EMBEDDED IEEE-488
PROGRAMMING INTERFACE
Document: 83-468-007 Rev B
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Fax: (732) 922-9334
Web: www.lambda-emi.com
Table of Contents
1. THE DIGITAL PROGRAMMING OPTION................................................... 1
1.1 OVERVIEW: IEEE AND RS-232 PORTS ........................................................1
1.2 SCOPE
1.3 USING
OF MANUAL ......................................................................................2
DIGITAL PROGRAMMING .................................................................2
1.3.1 THE IEEE-488.2 INTERFACE............................................................2
1.3.2 THE RS-232 INTERFACE ..................................................................2
1.3.3 IEEE AND RS-232 INTERACTION ....................................................2
1.4 CONFIGURING
THE IEEE INTERFACE.........................................................3
1.4.1 CONFIGURING THE IEEE CONTROLLER .......................................3
1.4.2 CONFIGURING THE IEEE INTERFACE ...........................................3
1.5 GETTING
STARTED WITH THE SOFTWARE................................................4
1.5.1 EXAMPLE SESSION USING THE ‘IBIC’ CONSOLE.........................4
1.5.2 EXAMPLE PROGRAM WRITTEN IN VISUAL BASIC .......................4
1.5.3 EXAMPLE PROGRAM WRITTEN IN LABVIEW ................................5
1.6 PROGRAMMING
VOLTAGE AND CURRENT ...............................................6
1.6.1 PROGRAM OUTPUT VOLTAGE .......................................................6
1.6.2 PROGRAM OUTPUT CURRENT.......................................................6
1.6.3 DISABLE THE SUPPLY OUTPUT .....................................................6
1.6.4 ENABLE THE SUPPLY OUTPUT ......................................................7
1.6.5 READ PROGRAMMING MODE .........................................................7
1.7 MEASURING
VOLTAGE AND CURRENT......................................................8
1.7.1 MEASURE VOLTAGE ........................................................................8
1.7.2 MEASURE CURRENT........................................................................8
1.7.3 SET MEASUREMENT FILTERING ....................................................8
1.8 LIMITS
AND PROTECTIONS..........................................................................9
1.8.1 SET VOLTAGE LIMIT.........................................................................9
1.8.2 SET CURRENT LIMIT ........................................................................9
1.8.3 OVER-VOLTAGE PROTECTION......................................................9
1.8.4 OVER-CURRENT PROTECTION ...................................................10
1.9 COMMON
COMMANDS................................................................................12
1.9.1 READ DEVICE IDENTITY ................................................................12
1.9.2 GO TO LOCAL..................................................................................12
1.9.3 REMOTE ENABLE ...........................................................................12
1.9.4 READ STATUS BYTE REGISTER...................................................12
1.9.5 RESET THE POWER SUPPLY........................................................13
1.9.6 CHANGING THE POWER-UP DEFAULTS......................................13
1.10 USING
ERROR AND STATUS REGISTERS ................................................13
1.10.1 OVERVIEW: REGISTER FAN-OUT.................................................14
1.10.2 GLOSSARY OF REGISTER TERMS...............................................14
1.10.3 CLEAR ALL STATUS REGISTERS .................................................17
1.10.4 SERIAL POLL AND STATUS BYTE REGISTER ...........................17
1.10.5 STANDARD EVENT STATUS REGISTER .....................................18
1.10.6 THE OPERATIONAL REGISTERS ..................................................19
1.10.7 THE QUESTIONALBE REGISTERS................................................21
2. THE RS-232 INTERFACE ......................................................................... 22
Document: 83-468-007 Rev B
2.1 CONFIGURING
2.1.1 THE RS-232 CABLE.........................................................................22
2.1.2 DEFAULT RS-232 CONFIGURATION.............................................22
2.2 RS-232
2.2.1 CHANGE CHARACTER ECHO........................................................24
2.2.2 GO TO LOCAL COMMAND..............................................................25
2.2.3 CHANGE THE BAUD RATE.............................................................25
2.2.4 CHANGE THE DATA BITS...............................................................25
2.2.5 CHANGE THE PARITY BITS ...........................................................26
2.2.6 CHANGE THE STOP BITS...............................................................26
2.3 ERROR
COMMAND SET ...............................................................................24
REGISTERS AND RS-232...............................................................27
THE RS-232 INTERFACE...................................................22
3. ADJUST THE IEEE CALIBRATION.......................................................... 28
3.1 INTRODUCTION ...........................................................................................28
3.2 CALIBRATE
3.3 CALIBRATE
3.4 CALIBRATE
3.5 CALIBRATE
THE VOLTAGE PROGRAMMING...........................................28
THE VOLTAGE MEASUREMENT...........................................30
THE CURRENT PROGRAMMING ..........................................31
THE CURRENT MEASUREMENT ..........................................32
4. SUMARY TABLE OF COMMANDS .......................................................... 35
List of Tables
Table 1. The *SAV 0 Command............................................ 13
Table 2. The Status Byte Register......................................... 17
Table 3. The Standard Event Status Register ....................... 18
Table 4. The Operational Registers....................................... 19
Table 5. Default RS-232 Configuration .................................. 22
Table 6. RS-232 Echo Settings ............................................. 24
List of Figures
Figure 1. IEEE Address Switch Settings ................................... 3
Figure 2. Status and Error Register Diagram.......................... 15
Figure 3. Status and Error Handler ......................................... 16
Figure 4. RS-232 Cable Construction ..................................... 23
Document: 83-468-007 Rev B
WARNING:
When a power supply with IEEE option is first powered ON, or when a
“Go To Local” command is sent, the supply output will jump to
whatever is set on the front panel knobs.
Therefore, it is recommended the front panel Voltage and Current
knobs be turned counter-clockwise to ZERO before REMOTE
programming.
1 THE DIGITAL PROGRAMMING OPTION
1.1 OVERVIEW: IEEE AND RS-232 PORTS
Most power supplies come standard with the Local and Analog Remote programming
modes which use the front panel knobs or the back panel 25 pin ‘D’ connector. A third
programming mode, Digital Remote, is available as an option. This option adds an embedded interface board with two extra connectors to the back of the supply.
The connectors allow cables to be run from the supply to a remotely located operator
terminal or to a computer running an automation program. A terminal allows the operator
to type commands to the power supply which take affect as soon as they are typed. An
automation program will allow several power supplies to be ‘daisy chained’ together. It
also allows other instruments, including relay switchers and measurement devices, to be
synchronized with the power supplies in complex power systems.
When the supply is running in the digital programming mode, the front panel knobs are
disabled but all the front panel indicators still show the status of the supply. The power
supply output levels and operating states may be monitored through the computer port.
Commands that are standard with digital programming include:
Introduction
1
• Program Voltage • Program Current
• Measure Voltage • Measure Current
• Set Maximum Voltage • Set Maximum Current
• Over-Voltage Shutdown • Over-Current Shutdown
• Error and Status Messages
• Computerized Calibration
• IEEE-488.2 Compliant • SCPI Compliant
Document: 83-468-007 Rev B
1.2 SCOPE OF MANUAL
This manual contains the information needed to setup and operate the embedded digital
interface used in the Lambda EMI power supplies including the EMS and ESS models.
The interface is contained on one circuit card. It may be optionally installed by Lambda
facilities at the time of purchase.
This manual does NOT include specifications for digital accuracy and response rate.
These values are only valid for the power supply in which the interface is installed, so
the specifications are given in the User Manual for the power supply.
1.3 USING DIGITAL PROGRAMMING
1.3.1 THE IEEE-488.2 INTERFACE
The IEEE-488 digital programming interface (also called the GPIB interface) is a popular
way to connect instruments to a computer. It uses a specialized 24-pin cable with connectors that allow cables to be ‘stacked’ together. There are eight data wires, eight control wires and eight ground wires. If the system runs from a personal computer, there are
numerous vendors of IEEE controller cards and software.
The IEEE-488 standard has gone through several upgrades. The IEEE-488.1 focused
on the handshaking of the eight control lines. The IEEE-488.2 added status registers inside each instrument and it added common commands to make programming groups of
instrument easier. The latest specification, SCPI, adds guidelines for the command syntax so one vendor’s power supply will use the same commands as another’s. The
Lambda interface follows all of these standards.
Because up to 15 instruments may be connected and independently controlled by a single IEEE controller, each instrument must have a unique address. On the power supply,
the address is set by a DIP switch accessible through a slot in the back panel.
Introduction
2
1.3.2 THE RS-232 INTERFACE
The second connector on the interface board is for the RS-232 serial port. It uses a
9-pin “D” connector. Only three wires are used: transmit data, receive data, and ground.
Compared to the IEEE port, the RS-232 is slower and it has limited status and error reporting. Also, there is no instrument addressing so only one power supply can be run
from each controller port. The advantage of RS-232 is the cable is easy to make and
every personal computer and terminal comes standard with it.
The RS-232 specification does not include any requirements for command syntax. For
this port, a “short form” command set is available where each command has only a couple of characters. The short form commands are easy to type into a terminal program.
1.3.3 IEEE AND RS-232 INTERACTION
When the power supply is first powered up, the RS-232 serial port is active. If a command is sent over the IEEE bus, the IEEE port becomes enabled and the RS-232 port
will no longer function. To restore the function to the RS-232 port, the power supply must
be cycled off and on.
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1.4 CONFIGURING THE IEEE INTERFACE
1.4.1 CONFIGURING THE IEEE CONTROLLER
A typical IEEE controller is a personal computer with a IEEE interface card. Each card
vendor supplies its own configuration instructions and interface software.
Each time the software is executed, the controller must be configured as follows:
Controller Address = 0. This is factory default for all controllers.
EOI Flag = TRUE. The “End or Identify” is a control line in the IEEE cable that
is asserted when the last character of a message string is sent. It is required
for Lambda EMI supplies
EOS Flag = FALSE: The “End of String” is used in some instruments to say a
character, such as a linefeed, marks the last character of a message. The
Lambda EMI supply does not require an end of string character.
1.4.2 CONFIGURING THE IEEE INTERFACE
The power supply is connected to the controller using a standard IEEE-488 cable. Standard connecting requirements are as follows:
Verify the power supply is switched OFF before connecting any cables to it.
ConfiguringBeginning Software
3
A maximum of 15 devices may be connected to any one IEEE bus. Maximum
cable length between any two devices should be six feet. Total cable length
should be less than 65 feet.
Before powering up the supply, set the IEEE address on its back panel switch.
It is labeled “IEEE ADDRESS”. Each device on the IEEE bus must have a
unique address. The controller is normally at address = 0 and address = 31 is
reserved, so the available addresses are from 1 to 30. See Figure 1.
Before powering up the supply, verify the FORCED LOCAL switch on IEEE
address switch is downward for OFF. Setting this switch ON will disable remote programming over the IEEE and RS-232 busses. See Figure 1.
Figure 1. IEEE Address Switch Settings
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1.5 GETTING STARTED WITH THE SOFTWARE
A computer can use a variety of controllers, programs, and programming languages for
the IEEE bus. Here are three examples showing minimal programs to set the voltage,
set the current and measure the voltage from a Lambda EMI power supply.
1.5.1 EXAMPLE SESSION USING THE ‘IBIC’ CONSOLE
A popular console program is National Instruments “Win32 Interactive Control” (file:
ibic.exe). As the operator types each command on the computer, at the colon prompt, it
is immediately sent to the power supply. This example works only for computers with
National Instruments and compatible IEEE controller cards.
Win32 Interactive Control
Copyright 1996 National Instruments Corporation
All rights reserved.
Type 'help' for help or 'q' to quit.
: ibdev Controller address
enter board index: 0
enter primary address: 4
enter secondary address: 0
enter timeout: 13
enter 'EOI on last byte' flag: 1
enter end-of-string mode/byte: 10
ud0: ibwrt "sour:volt 100"
[0100] ( cmpl )
count: 12
Program supply to
ud0: ibwrt "sour:curr 5"
[0100] ( cmpl )
count: 11
ud0: ibwrt "meas:volt?" output voltage?”
[0100] ( cmpl )
count: 10
ud0: ibrd 50
[2100] ( end cmpl )
count: 11
31 30 30 2e 30 38 33 31 1 0 0 . 0 8 3 1
30 31 0a 0 1 .
Supply reported output voltage
Supply Address on DIP Switch
Program supply to
100 volts output
5 amps output
Query: “What is
Read response
4
1.5.2 EXAMPLE PROGRAM WRITTEN IN VISUAL BASIC
Microsoft’s Visual Basic is a windows programming language that may be used to create
“virtual instruments” and automation programs. Here is a simple program which sends
commands to a Lambda EMI power supply to set the voltage, set the current and measure the voltage. The program’s window only conatains two items: a “Start” button and a
text box to show the measured voltage. The syntax of the CALLed functions are correct
only for National Instruments and compatible IEEE controllers. Don’t forget to add the
forms “Ni-global.bas” and “Vbib-32.bas” to you project.
Document: 83-468-007 Rev B
Beginning Software
Example Program Written in Visual Basic
Option Explicit
Dim LambdaUD As Integer 'supply device descriptor
Dim strMeasVolt As String * 50 'buffer for reading input message
Private Declare Function GetTickCount Lib "kernel32" () As Long
Private Sub cmdStart_Click()
'start program here after "Start" button clicked
'open IEEE port, get "User Device Description" = LambdaUD
'assume power supply address is set to "4" on DIP switch
Call ibdev(0, 4, 0, T3s, 1, 10, intLambdaUD)
Call ibwrt(LambdaUD, "volt 100") 'program output to 100 volts
Call ibwrt(LambdaUD, "curr 2") 'program output to 2 amps
Wait 500 'wait 0.5 sec for output to settle
Call ibwrt(LambdaUD, "meas:volt?") 'ask "What is output voltage?"
Call ibrd(LambdaUD, strMeasVolt) 'read back output voltage
txtOutVolt.Text = strMeasVolt 'display output voltage on window
End Sub
Private Sub Wait(mSecWait As Long)
'subroutine to wait "mSecWait" milliseconds
Dim StartTime As Long
StartTime = GetTickCount
Do
Loop While (GetTickCount - StartTime < mSecWait)
End Sub
5
1.5.3 EXAMPLE PROGRAM WRITTEN IN LABVIEW
The National Instruments LabVIEW programming language is a popular language which
is optimized for instrument control and data analysis. It is a graphical language where
functions are shown as icons with connection points and data flows along drawn lines.
Here is a simple program which sends commands to a Lambda EMI power supply to set
the voltage, set the current and measure the voltage. The program’s window only conatains two items: a numeric control for the supply IEEE address and a text indicator to
show the measured voltage.
Document: 83-468-007 Rev B
Program OutputBeginning Software
1.6 PROGRAMMING VOLTAGE AND CURRENT
1.6.1 PROGRAM OUTPUT VOLTAGE
The output voltage can be programmed by sending the command:
SOURCE:VOLTAGE:AMPLITUDE <nn.nn>
where <nn.nn> is any valid voltage with or without decimal places. There must be a
space before the number.
Per the Summary Table in Section 4, the command can be abbreviated in any of the following ways:
SOUR:VOLT:AMPL <nn.nn>
SOUR:VOLT <nn.nn>
VOLT:AMPL <nn.nn>
VOLT <nn.nn>
The power supply output will not reach the programmed voltage until a Program Current
command is also sent. To get the sharpest transition from zero to programmed output,
disable the output (Section 1.6.3), program voltage and current, then enable the output.
If the voltage is more than the supply output or less than zero, the command will be ignored and the Command Error bit of the Standard Event Status Register will be set. If
the voltage is higher than the limit set by the SOURCE:VOLTAGE:LIMIT value, the
command will be ignored and the Execution Error bit of the Standard Event Status Register will be set.
To read what voltage the supply was programmed to, regardless of the actual voltage,
send query SOUR:VOLT:AMPL? and read the response message.
The short form of “program voltage” is: PV <nn.nn>
6
1.6.2 PROGRAM OUTPUT CURRENT
The output current is programmed by sending the command:
SOURCE:CURRENT:AMPLITUDE <nn.nn> or “CURR” <nn.nn>
where <nn.nn> is any valid current with or without decimal places. There must be a
space before the number.
The power supply output will not reach the programmed current until a program voltage
command is also sent. To get the sharpest transition from zero to programmed output,
disable the output (Section 1.6.3), program voltage and current, then enable the output.
If the <nn.nn>is more than the supply output or less than zero, the command will be ignored and the Command Error bit of the Standard Event Status Register will be set. If
the current is higher than the limit set by the SOURCE:CURRENT:LIMIT value, the
command will be ignored and the Execution Error bit of the Standard Event Status Register will be set.
To read what current the supply was programmed to, regardless of the actual output current, send query SOUR:CURR:AMPL? and read the response message.
The short form of “program current” is: PC <nn.nn>
1.6.3 DISABLE THE SUPPLY OUTPUT
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The power supply output can be shut off by sending this command:
SOURCE:VOLTAGE:OUTPUT OFF or VOLT:OUT OFF
This command will not disconnect the supply output. It is equivalent to programming the
output to zero volts.
To read if the supply output is disabled, send query VOLT:OUTP?. A “0” (zero) will be
returned if the output is disabled.
The short form for “supply off” is: SF
1.6.4 ENABLE THE SUPPLY OUTPUT
After the supply output has been shut off with the SOUR:VOLT:OUTP OFF command,
the output can be turned back on by sending this command:
SOURCE:VOLTAGE:OUTPUT ON or VOLT:OUTP ON
The output will immediately jump to the last programmed voltage and current.
To read if the supply output is enabled, send query VOLT:OUTP?. A “1” (one) will be returned if the output is enabled.
The short form for “supply on” is: SN
1.6.5 READ PROGRAMMING MODE
7
The power supply may be programmed in two modes. In Local Mode, the front panel
knobs or back panel analog connections set the supply output. In Remote Mode, the
IEEE/RS232 interface sets the output. The mode is indicated by the front panel
REMOTE LED (if it is installed). The mode may be read by sending this query:
SYSTEM:PROGMODE? or SYST:PROG?
The response will be one of three choices: LOCAL, REMOTE, OR FORCED_LOCAL.
Since sending a query takes the supply out of Local Mode, that response will not be received. The Forced Local Mode is set by the first rocker on the IEEE address switch
(see Figure 1).
The short form for this command is: MH?
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1.7 MEASURING VOLTAGE AND CURRENT
1.7.1 MEASURE VOLTAGE
The output voltage can be measured by sending the command:
MEASURE:VOLTAGE? or MEAS:VOLT?
When the controller does the next IEEE Read, the supply will send the measured voltage to it. The measurement is always given to six decimal places even if the measurement is not so accurate. See the Specifications Section in the power supply User Manual
for actual measurement accuracy. If the back panel analog connector is wired for Remote Voltage Sensing, the measured value will be the voltage at the sense lines, not the
voltage at the supply output.
The short form for “measure voltage” is MV?
1.7.2 MEASURE CURRENT
The output current can be measured by sending the SCPI command:
MEASURE:CURRENT? or MEAS:CURR?
When the controller does the next IEEE Read, the supply will return the amperes of current being produced. The measurement is always given to six decimal places even if the
measurement is not so accurate. See the Specifications Section in the power supply
User Manual for actual measurement accuracy.
The short form for “measure current” is: MC?
Measure Output
8
1.7.3 SET MEASUREMENT FILTERING
The output voltage or current may be queried with MEAS:VOLT? or MEAS:CURR?. Because of noise, the measurements may have unacceptable random variations. Therefore, a routine is implemented so the board makes measurements every 16 milliseconds
and keeps a running average of the output.
The number of samples in the running average may be adjusted. A higher number will
“smooth” constant output readings but it will slow down the reported response to actual
changes in output.
The voltage measurement averaging is set by the command:
AFV nnn
Where nnn is a number between 1 and 250. The default is 20.
The current measurement averaging is set by the command:
AFC nnn
Where nnn is a number between 1 and 250. The default is 20.
Changing the averaging value will not slow down the bus speed or slow down the response time to an over-voltage and over-current shutdown.
Any changes in AFV or AFC may be made the power-up default by sending the *SAV 0
command.
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1.8 LIMITS AND PROTECTIONS
1.8.1 SET VOLTAGE LIMIT
The maximum voltage that may be programmed to the power supply is set by the following command. It does not monitor the actual output voltage. It only inspects the numeric
value in a voltage programming command.:
SOURCE:VOLTAGE:LIMIT <nn.nn> or VOLT:LIM <nn.nn>
where <nn.nn> is a number between zero and the maximum supply output voltage. The
decimal is optional.. A space is required before the number.
By default, the voltage limit equals the power supply maximum voltage. A new voltage
limit will remain in effect until the supply power is switched off. A new voltage limit can be
made to be the power-up default by following VOLT:LIM with the *SAV 0 command.
See Section 1.9.6 for a description of the *SAV 0 command.
If a command is sent to set the supply to a voltage higher than the voltage limit, the
command will be ignored and the Execution Error bit of the Standard Event Status Register will be set.
To read what voltage limit has been set, send query VOLT:LIM? and read the response
message.
The short form for “set voltage limit” is: SVL <nn.nn>
Limit Output
9
1.8.2 SET CURRENT LIMIT
The maximum current that may be programmed to the power supply is set by the following command. It does not monitor the actual output current. It only inspects the numeric
value in a current programming command.
SOURCE:CURRENT:LIMIT <nn.nn> or CURR:LIM <nn.nn>
where <nn.nn> is a number between zero and the maximum supply output current in
amperes. The decimal is optional.. A space is required before the number.
By default, the current limit equals the power supply maximum current. A new current
limit will remain in effect until the supply power is switched off. A new current limit can be
made to be the power-up default by following CURR:LIM with the *SAV 0 command.
See Section 1.9.6 for a description of the *SAV 0 command.
If a command is sent which sets the supply to a current higher than the current limit, the
command will be ignored and the Execution Error bit of the Standard Event Status Register will be set.
To read what current limit has been set, send query CURR:LIM? and read the response
message.
The short form for “set current limit” is: SCL <nn.nn>
1.8.3 OVER-VOLTAGE PROTECTION
Lambda supplies feature two types of over-voltage protection that shuts down the output
if the output exceeds some settable voltage level. The analog method uses the OverVoltage Adjustment potentiometer on the front panel. The digital method uses the IEEE
board to constantly sample the supply output voltage. The analog pot setting always
takes priority over any digital programmed level. Therefore, for digital over-voltage protection, it is recommended the potentiometer be turned clockwise to maximum.
Document: 83-468-007 Rev B
Using IEEE protection, the time between an over-voltage occurring and the supply shutting down is typically 20 milliseconds. This is the time for two successive readings to exceed the limit. The analog protection responds much faster. There is no analog overcurrent protection.
IEEE over-voltage protection is implemented with four commands:.
1.8.3.1 Set the over-voltage threshold:
SOURCE:VOLTAGE:LEVEL <nn.nn> or VOLT:LEV <nn.nn>
where <nn.nn> is a number between zero and the maximum supply output voltage. The
decimal is optional.The voltage may be more or less than the limit set by the
SOURCE:VOLTAGE:LIMIT command described in the previous paragraphs.
The set voltage level may be read by sending the query VOLT:LEV? and reading the response number.
The short form for “set voltage protection level” is: SVPL <nn.nn>
1.8.3.2 Enable the protection:
SOURCE:VOLTAGE:STATE ON or VOLT:STAT ON
The protection can be disabled by specifying OFF instead of ON.
The state of the protection may read by sending the query VOLT:STAT? and reading the
response. A “1” (one) means the protection is enabled..
The short form for “set voltage protection state” is: SVPS ON (or OFF)
Limit Output
10
1.8.3.3 Query for over-voltage shutdown:
SOURCE:VOLTAGE:TRIPPED? or VOLT:TRIP?
Read the response number. The normal response is “0” (zero). If a “1” (one) is returned,
it means an over-voltage has occurred and the output is shut down.
The response number is actually the value of the Operational Condition Register Bit 0.
Because an over-voltage can set bits in four IEEE registers, it is recommended that a
*CLS be sent to clear them after an over-voltage occurs. See the Section 0 on Status
and Error Register Programming for more details.
The short form for “set voltage protection tripped?” is: SVPT?
1.8.3.4 Reset after shutdown:
SOURCE:VOLTAGE:CLEAR or VOLT:CLE
After an over-voltage shut down has occurred, this command must be sent to clear the
error status before any new voltage commands will be accepted.
If and over-voltage is not cleared, and a new voltage command is sent, the command
will be ignored and the Command Error bit in the Standard Event Status Register will be
set.
The short form for “set voltage protection clear” is: SVPC
1.8.4 OVER-CURRENT PROTECTION
The IEEE Interface board constantly measures the power supply output current and the
board can be set to shut down the supply if the output current exceeds a settable level.
The time between an over-current occurring and the supply shutting down is typically
20 milliseconds.
Document: 83-468-007 Rev B
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