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Model 5802
IEEE-488 Interface
Instruction Manual
Contains Operating and Servicing Information
WARRANTY
Keithley Instruments, Inc. warrants this product to be free from defects in material and workmanship for a period of 1 year from date of
shipment.
Keithley Instruments, Inc. warrants the following items for 90 days from the date of shipment: probes, cables, rechargeable batteries,
diskettes, and documentation.
During the warranty period, we will, at our option, either repair or replace any product that proves to be defective.
To exercise this warranty, write or call your local Keithley representative, or contact Keithley headquarters in Cleveland, Ohio, You will
be given prompt assistance and return instructions. Send the product, transportation prepaid, to the indicated service facility. Repairs
will be made and the product returned, transportation prepaid. Repaired or replaced products are warranted for the balance of the origi-
nal warranty period, or at least 90 days.
LIMITATION OF WARRANTY
This warranty does not apply to defects resulting from product modification without Keithley's express written consent, or misuse of
any product or part. This warranty also does not apply to fuses, software, non-rechargeable batteries, damage from battery leakage, or
problems arising from normal wear or failure to follow instructions.
THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING ANY IMPLIED
WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. THE REMEDIES PROVIDED HEREIN ARE
BUYER'S SOLE AND EXCLUSIVE REMEDIES.
NEITHER KEITHLEY INSTRUMENTS, INC. NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT, INDI-
RECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS INSTRUMENTS AND
SOFTWARE EVEN IF KFJTHLEY INSTRUMENTS, INC., HAS BEEN ADVISED IN ADVANCE OF THE POSSIBILITY OF
SUCH DAMAGES. SUCH EXCLUDED DAMAGES SHALL INCLUDE, BUT AR!? NOT LIMITED TO: COSTS OF REMOVAL
AND INSTALLATION, LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON, OR DAMAGE TO PROPERTY.
Model 5802 IEEE-488 Interface
Instruction Manual
0 1985, Keithley Instruments, Inc.
Test Instrumentation Group
All rights reserved.
Cleveland, Ohio, U.S.A.
July 1987, Second Printing
Document Number: 5802-901-01 Rev. 6
Safety Precautions
The following safety precautions should be observed before Do not exceed the maximum signal levels of the instruments
using this product and any associated instrumentation. Al- and accessories, as defined in the specifications and operating
though sane instruments and accessories would normally be information, and as shown on the instrument or test fixture
used with non-hazardous voltages, there are situations where rear panel, or switching card.
hazardous conditions may be present.
Do not connect switching cards directly to unlimited power
This product is intended for use by qualified personnel who circuits. They are intended to be used with impedance limit-
recognize shock hazards and are familiar with the safety pre- ed sources. NEVER connect switching cards directly to AC
cautions required to avoid possible injury. Read the operating main. When connecting sources to switching cards, install
information carefully before using the product. protective devices to limit fault current and voltage to the
card.
Exercise extreme caution when a shock hazard is present. Le-
thal voltage may be present on cable connector jacks or test When fuses are used in a product, replace with same type and
fixtures. The American National Standards Institute (ANSI) rating for continued protection against fire hazard.
states that a shock hazard exists when voltage levels greater
than 3OV RMS, 42.4V peak, or 60VDC are present. A good Chassis connections must only be used as shield connections
safety practice is to expect that hazardous voltage is present for measuring circuits, NOT as safety earth ground connec-
in any unknown circuit before measuring. tions.
Before operating an instrument, make sure the line cord is If you are using a test fixture, keep the lid closed while power
connected to a properly grounded power receptacle. Inspect is applied to the device under test. Safe operation requires the
the connecting cables, test leads, and jumpers for possible use of a lid interlock.
wear, cracks, or breaks beforr each use.
If a @screw is present on the test fixture, connect it to safety
For maximum safety, do not touch the product, test cables, or earth ground using #18 AWG or larger wire.
any other instruments while power is applied to the circuit
under test. ALWAYS remove power from the entire test sys-
The $ symbol on an instrument or accessory indicates that
tem and discharge any capacitors before: connecting or dis-
1OOOV more may be present on the terminals. Refer to the
or
connecting cables or jumpers, installing or removing
product manual for detailed operating information.
switching cards, or making internal changes, such as install-
ing or removing jumpers.
Instrumentation and accessories should not be connected to
humans.
Do not touch any object that could provide a current path to
the common side of the circuit under test or power line
(earth) ground. Always make measurements with dry bands Maintenance should be performed by qualified service per-
while standing on a dry, insulated surface capable of with- sonnel. Before performing any maintenance, disconnect the
standing the voltage being measured. line cord and all test cables.
SPECIFICATIONS/5802
ANALOG OUTPUT
LEVEL:1" = 10,cal CO""tS Xl gain.
0" TIME:FdlOWS
RESPONSE cnnversion
d,splay rate,
1" = 100Counts Xl00 gain,
on OUTPUT RESISTANCE: 1OOOn~
Maximurn output voltage = *`iv. ISOLATION: ANALOC; OUTPUT LO is connected to ,EEE COM-
ACC"RACY: *(0.25% 0, displayed reading +*r"")~ In x100. 2mV MON. Maximum cwnmo" mode voltage from IEEE COMMON to
output = 0.2 displayed aunts. earth ground is 3W rms al dc. 50 or 6011~~
:EEE-488 BUS IMPLEMENTATION
.l"l.T,LINE COMMANDS: DCL. SK, GET. GTL. UNT. UNL. TRIGGER:
WE. 3'". LLO, TO = Continuous on Talk
lN,L,NE COMMANDS: IFC, EN, EOI, SRQ, ATN, T, = One-shot on Talk
T2 = Continuous ~1" GET
NTERFACE FUNCTIONS: SHl. AH,. T5, TEO. L4. LEO, SRI. RLO.
T3 = O"e~shr,t <>n GET
PPO. DC,, DT,, CU. El.
T4 = Cantinuous on X
`ROCRAMMABLE PARAMETERS: Range. DRY CIRCUIT TZ = One-shut on X
TEST,Operate, RELative. POLARITY, DRIVE. TRlCger. Calibra-
EXECUTE:
tian. EOI, SRQ. Status. Data Format. Terminatar~
X = Exerute drviwdcprndent cwnmands
,E",CE-DEPENDENT COMMANDS:
EO,:
RANGE: KO = EOI Enabled
NON K1 = EO, "isabied
DRY CIRCUIT DRY CIRCUIT
STATUS WORD:
TEST TEST
ti" = Ourput status word,
RO A"to Auto
DATA FORMAT:
2""rnII 2OOmll
GO = Readings and status word with preiix
;: 2 R 2 0
C, = Readings and status word withut pretix
R-3 20 n 20 0
114 200 n 20 0 SRQ:
R5 2k n 20 n MO = Clear SRQ Data Mask
20 0 MI = Reading Overthn%
Rb 2Ok n
20 0 MS i Reading D""r
R7 200k n
M9 = Reading Done or Reading Ovcrfh
RELATIVE:
Ml6 = BUS)
ZO = REL ofi M,, = Busy ,,T Reading Overflw
Z, = REL on
M24 = Busy or Reading Dane
OPERATE: M25 = Busy. Reading hne i)r Reading Overflw
0" = STBY (Standby1 M32 = Clear SRQ Ermr Mask
0, = OPR (Operatv) M33 = IDDCO
POLARITY: M34 = IDDC
PO = FOL + M3S = ,DDC or IDDCO
Pi = I'OL - M36 = Not in Remote
DRIVE: ,437 = Not in Remok or ,DDCCl
DO = DRIVE (puked) M3X = Not in Rem<>tr or ,D,,C
D, = DRIVE M39 = Not in Remote. lDDC or ("DC0
(dc)
DRY ClRCUIT TEST: TERMINATOR:
CO = NON DRY CIRCUIT TEST Y(ASC,I) = ASCII Character
C, = DRY CIRCUIT TEST Y(LF) = CR LF
Y(CR) = LF CR
D,G,TAL CALIBRATION:
Y(DEL, = None
v * n.nn,,,,~ * nn = enter calibratiun value.
T,ME FROM TRlGGER TO FlRST BYTE OUT: 350"~s 10 500ms.
STORE:
LO = Store calibration constants. ADDRESS MODES: Taik Only. Addressable
DATA FORMAT AND STATUS BYTE OUTPUT
DATA FORMAT: STATUS BY-I-E OUTPUT:
I
TERMINATOR I PREFIX
EXPONENT DRIVE
POLARITY
PREF'X -FL u-l DRY CIRCUIT TEST
N + DP + I.23456 E + 2 ,cR)(LF, OPERATE
RANGE
(pulsed)
D = DRIVE id4 580 D P C 0 R Z K T Md Me H Y
S=STANDBY J L DRY CIRCUIT TEST: N = NON DRY
N = NORMAL CIRCUIT TEST
O=OVERFLOW D=DRY
RELATIVE
Z = RELATIVE CIRCUIT TEST
EOI
!- POLARITY: + = POL +
TRIGGER
- =POL -
SRQ ON DATA
SRQ ON ERROR
LINE FREQUENCY A
TERMINATOR
TABLE OF CONTENTS
SECTION l-GENERAL INFORMATION
1.1 INTRODUCTION ...... ...... ...... 1-l
1.2 INTERFACE FEATURES ...... ...... ...... 1-l
1.3 WARRANlY INFORMATION ...... ...... ...... 1-l
1.4 MANUAL ADDENDA ...... ...... ..,... 1-l
1.5 SAFETY SYMBOLS AND TERMS ...... ...... ...... 1-l
1.6 USING THE INSTRUCTION MANUAL ...... ...... ...... 1-l
1.7 SPECIFICATIONS ...... ...... ...... l-2
1.8 UNPACKING AND INSPECTION.. ...... ...... ...... l-2
SECTION 2-AN OVERVIEW OF THE IEEE-488 BUS
2.1 INTRODUCTION ............................................................................ 2.1
2.2 BUS DESCRIPTION .......................................................................... 2-l
2.3 IEEE-488 BUS LINES ......................................................................... 2-2
2.3.1 BusManagement Lines ..................................................................... 2-2
2.3.2 Handshake Lines ........................................................................... 2-2
2.3.3 Data Lines ................................................................................. 2-3
2.4 BUS COMMANDS ........................................................................... 2.3
2.4.1 UniIine Commands ......................................................................... 2-4
2.4.2 Universal Commands ....................................................................... 2-4
2.4.3 Addressed Commands ...................................................................... 2-5
2.4.4 Unaddressed Commands ................................................................... 2-5
2.4.5 Device-Dependent Commands .............................................................. 2-5
2.5 COMMAND CODES ......................................................................... 2.5
2.6 COMMAND SEQUENCES ................................................................... 2-7
2.6.1 Addressed Command Sequence ............................................................. 2-7
2.6.2 Universal Command Sequence .............................................................. 2-8
2.6.3 Device-Dependent Command Sequence ...................................................... 2-8
SECTION 3-SYSTEM CONFIGURATION
3.1 INTRODUCTION ............................................................................ 3-l
3.2 HARDWARE CONSIDERATIONS ............................................................. 3-l
3.2.1 Typical Systems ............................................................................ 3-l
3.2.2 Bus Connections ........................................................................... 3-2
3.2.3 Primary Address Selection.. ................................................................ 3-4
3.3 SOFTWARE CONSIDERATIONS ............................................................. 3-5
3.3.1 Controller Interface Routines ................................................................ 3-5
3.3.2 HP-85BASIC Statements ................................................................... 3-5
3.3.3 InterfaceFunction Codes .................................................................... 3-6
3.3.4 Interface Commands ....................................................................... 3-7
I
SECTION 4-OPERATION
4.1 INTRODUCTION .............. ....... ...... ...... 4-l
4.2 GENERAL BUS COMMANDS ....... ...... ...... 4-l
4.2.1 REN (Remote Enable). ........ ....... ...... ...... 4-l
4.2.2 IFC (Interface Clear) .......... ....... ...... ...... 4-2
4.2.3 GTL (Go To Local) ........... ....... ...... ...... 4-2
i.2.4 LLO (Local Lockout). ......... ...... 4-2
4.2.5 DCL (Device Clear). .......... ....... ...... ...... 4-3
4.2.6 SDC (Selective De&ce Clear) ...... 4-3
4.2.7 Serial Polling (SPE, SPD) ...... 4-3
4.3 DEVICE-DEPENDENT COMMAND PROGRAMMING.. ...... 4-4
4.3.1 Execute(X) .......................... .......... 4-b
4.3.2 Range (R) ........................... .......... ...... 4-6
4.3.3 Operate/Standby (0) ................. .......... ...... 4-6
4.3.4 Dry Circuit Test (C) .................. .......... 4-6
4.3.5 Relative (2). ......................... .......... ...... 4-7
4.3.6 Digital Calibration (V) and Storage (L) .......... ...... 4-7
4.3.7 Polarity (P) .......................... .......... ...... 4-8
4.3.8 Drive (D) ............................ ...... 4-8
4.3.9 Triggering (T) ............................ ................................................. 4-8
4.3.10 EOI (K) ................................. ................................................. 4-8
4.3.11 SRQ Mode (M) and Status Byte Format .... ................................................. 4-9
4.3.12 Status Word (U) or Alternate Output ...... ................................................ 4-13
4.3.13 Prefix(G) ................................................................................. 4-13
4.3.14 Programmable Terminator (Y) .............................................................. 4-14
4.3.15 Data Format .............................................................................. 4.14
4.4 TALK ONLY OPERATION .................................................................. 4.15
SECTION 5-ANALOG OUTPUT
5.1 INTRODUCTION ............................................................................ 5-l
5.2 USING THE ANALOG OUTPUT ............................................................. 5-l
5.3 OUTI'UTRESISTANCE ...................................................................... 5-3
5.4 Xl00 RESOLUTION AND ACCURACY ........................................................ 5-3
SECTION 8-PRINCIPLES OF OPERATION
6.1 INTRODUCTION ............................................................................ b-1
6.2 CIRCUIT DESCRIPTION ..................................................................... 6-l
6.2.1 Power Supply ............................................................................. 6-l
6.2.2 Digital Circuitry.. .......................................................................... 6-2
6.2.3 Analog Output ............................................................................. 6-2
SECTION 7-MAINTENANCE
7.1 INTRODUCTION ............................................................................ 7-l
7.2 INSTALLATION ............................................................................. 7-l
7.3 CALIBRATION .............................................................................. 7-l
7.3.1 Warm Up ................................................................................. 7-l
7.3.2 Recommended Calibration Equipment ........................................................ 7-l
7.3.3 Environmental Conditions .................................................................. 7-3
7.3.4 Calibration. ................................................................................ 7-3
7.4 SPECIAL HANDLING OF STATIC-SENSITIVE DEVICES ....................................... 7-3
7.5 TROUBLESHOOTING ....................................................................... 7-3
ii
SECTION 8--REPLACEABLE PARTS
8.1 INTRODUCTION ............................................................................ 8-l
8.2 REPLACEABLE PARTS. ...................................................................... 8-l
8.3 ORDERING INFORMATION ................................................................. 8-1
8.4 FACTORY SERVICE ......................................................................... 8-l
8.5 SCHEMATIC DIAGRAMS AND COMPONENT LOCATION DRAWINGS ........................ 8-1
iii
LIST OF TABLES
SECTION 2-AN OVERVIEW OF THE IEEE-488 BUS
2-l IEEE-488 Bus Command Summary .,,,...,,.._...,,,.,..,,,._..................,,............. 2-4
2-2 Hexadecimal and Decimal Command Codes.. 2-7
2-3 Typical Addressed Command Sequence.. 2-8
2-4 Typical Device-Dependent Command Sequence 2-8
SECTION 3-SYSTEM CONFIGURATION
3-l IEEE-488 Contact Designations ................................................................ 3-3
3-2 Primary Address Switch Positions ............................................................. 3-4
3-3 HP-85 IEEE-488 BASIC Statement ............................................................. 3-6
3-4 Interface Function Codes ....................................................... ............. 3-7
3-5 IEEE-488 Command Groups .................................................................. 3-7
SECTION 4-OPERATION
4-l GeneralBus Commands ...................................................................... 4-l
4-2 Default Values (Status Upon Power Up or After SDC or DCL). .................................. 4-4
4-3 Device-Dependent Command Summary ........................................................ 4-5
4-4 RangeCommands ........................................................................... 4-6
4-5 SRQMask Commands ....................................................................... 4-9
4-6 Status Byte and Mask Interpretation .......................................................... 4-10
SECTION t&ANALOG OUTPUT
5-l AnalogOutputParameters.................................................................... 5-3
SECTION 7--MAINTENANCE
7-1 Static SensitiveDevices....................................................................... 7-3
7-2 Model5802InterfaceChecks.................................................................. 7-4
SECTION 8-REPLACEABLE PARTS
8-l Model5802Parts List _...._.........................._.,.,.___.,...._.._.__._................ 8-2
iv
LIST OF ILLUSTRATIONS
SECTION 2-AN OVERVIEW OF THE IEEE-488 BUS
2-l IEEE-488 Bus Configuration ...... .. ......................... ..................... 2-l
2-2 Handshake Sequence ......................................................................... 2-3
2-3 Command Codes ............ _...... ........................................................ 2-6
SECTION 3-SYSTEM CONFIGURATION
3-l SystemTypes ...................................................... 3-l
3-2 IEEE-488 Connector ................................................. 3-2
3-3 IEEE-488 Connections ............................................... 3-2
3-4 Contact Assignments ................................................ 3-2
3-5 Rear Panel of Model 580 Showing IEEE-488 Connections and Switches 3-3
3-6 Typical IEEE-488 Bus Drive (one of 16). ............................... 3-3
3-7 Primary Address Switch (Address 25 Shown) ......................... 3-4
SECTION 4-OPERATION
4-l Status Byte Format .......................................................................... 4-10
4-2 General Format for UO Command ............................................................ 4-11
4-3 Data Format ................................................................................ 4-14
SECTION 5-ANALOG OUTPUT
5-l Analog Output Connections .................................................................. 5-l
5-2 Xl Analog Output ........................................................................... 5-2
5-3 XlOOAnalog Output .._ ...................................................................... 5-3
SECTION 6-PRINCIPLES OF OPERATION
6-l Simplified Block Diagram.. ................................................................... 6-l
6-2 Memory Map ................................................................................ 6-2
6-3 Xland Xl00 Gains ........................................................................... 6-3
SECTION 7-MAINTENANCE
7-l Model 5802 Installation ....................................................................... 7-2
SECTION 8-REPLACEABLE PARTS
8-l Model 5802 Interface, Component Location Drawing, Dwg. No. 5802-100 ......................... 8-4
8-2 Model 5802 Interface, Schematic Diagram, Dwg. No. 5802-106 ................................... 8-5
SECTION 1
GENERAL INFORMATION
1.1 INTRODUCTION 1.4 MANUAL ADDENDA
The Model 5802 is an IEEE-488 interface for the Model 580 Information concerning improvements or changes to the
Micro-ohmmeter. This interface, which includes analog instrument which occur after the printing of this manual
output, adds extra versatility to the Model 580 by allow- may be found on an addendum included with this
ing the transmission of data and commands over the manual. Review these changes before programming the
IEEE-488 bus. The interface provides all the necessary logic Instrument.
to interface the Model 580 to the bus using standard
IEEE-488-1978 protocol.
1.5 SAFETY SYMBOLS AND TERMS
1.2 INTERFACE FEATURES The following safety symbols and terms are used in this
manual and may be found on the instrument.
Important IEEE-488 interface features:
l With the Model 5802 installed, the Model 580 is able to The A symbol on the instrument indicates that the user
communicate with other insrmmentation using the same should refer to the operating instructions.
IEEE-488s1!778 standards.
l A standard IEEE-488 connector that provides easy con-
nection to the IEEE-488 bus. Information associated with the WARNING heading ex-
l An easily-changeable primary address. Although the plains dangers that could result in personal injury or
Model 580 is shipped from the factory with a primary death.
address of 25, the customer can change it by using the
five rear panel address switches.
Information following the CAUTION heading explains
l All Model 580 operation is supported by IEEE-488 pro-
hazards that could damage the instrument.
gramming. In addition, numerous other IEEE-488 com-
mands add operating features not available from the front
pSW1.
1.6 USING THE INSTRUCTION MANUAL
1.3 WARRANTY INFORMATION This manual contains all the information you need to con-
nect the Model 5802 to the IEEE-488 bus and program the
Warranty information may be found on the inside front instrument from a separate bus controller.
cover of this manual. Should it become necessary to exer-
cise the warranty, contact your Keithley representative or
The manual is divided into the following sections:
the factory to determine the proper course of action.
Keithley Instruments, Inc. maintains service facilities in the
1. Section 2 contains a general description of the IEEE-488
United States, the United Kingdom and throughout
bus and its commands.
Europe. Addresses for these facilities may be found inside
the front cover of this manual. Information concerning the 2. Section 3 contains information necessary to connect the
application, operation or service of your instrument may instrument to the bus and set the primary address.
be directed to the applications engineer at any of these 3. Section 4 contains the bulk of the programming infor-
locations. mation. General bus commands as well as commands
unique to the Model 5802 are covered in detail.
1-l
4. Section 5 explains the analog output feature of the and electrically before shipment. When the Model 5802
Model 5802. arrives, carefully unpack all items and check for any ob-
5. Section 6 contains Principles of Operation. vious signs of damage.
6. Section 7 contains maintenance information such as in-
stallation and troubleshooting.
Report any damage to the shipping agent immediately. Re-
7. Section 8 contains replaceable parts information and ap- tain and use the original packing material in case reship-
plicable schematics and component layouts. ment is necessary. The following items are shipped with
every Model 5802 order:
1.7 SPECIFICATIONS Model 5802 IEEE-488 Interface
Hardware necessary for installation
A complete list of IEEE-488 specifications can be found Model 5802 Instruction Manual
preceding this section. Additional accessories as ordered
1.8 UNPACKING AND INSPECTION If you need another manual, order the manual package
(Keithley Part No. 5802-901-01). This package includes an
The Model 5802 was carefully inspected both mechanically instruction manual and any pertinent addenda.
l-2
SECTION 2
AN OVERVIEW OF THE IEEE-488 BUS
2.1 INTRODUCTION
The IEEE-488 bus is an instrumentation data bus adopted
TO OTHER DEVlCES
by the IEEE (Institute of Elechical and Eleckonic Engineers)
/ * \
in 1975 and given the IEEE-488 designation. The most re-
cent revision of bus standards was made in 1978; hence
the complete description for current bus standards is the
IEEE-488-1978 designation.
The information presented here is not an elaborate descrip-
tion of a complicated set of standards. Rather, this section
briefly describes general bus structure including a bus com-
mand outline. Complete IEEE-488 bus information is
DATA BYTE
available from the IEEE and other sources. TRANSFER
CONTROL
2.2 BUS DESCRIPTION
The IEEE-488 bus is a parallel data transfer medium that INTERFACE
T
optimizes data transfer without using an excessive number
of bus lines. The bus has only eight data lines, used for
data and certain commands. In addition, the IEEE-488 bus
employs eight signal lines, including five bus management
lines and three handshake lines. Since the bus is of pamlIe
design, all devices connected to the bus have the same in-
formation available simultaneously. Each device processes
information received from the bus depending on its
capabilities.
HANDSHAKE
A typical bus configuration for controlled operation is
shown in Figure 2-l. A typical system has one controller BUS
and one or more instruments that receive commands and MANAGEMENT
which usually yield data.
Figure 2-1. IEEE-488 Bus Configuration
2-1
AN OVERVIEW OF THE IEEE-488 BUS
Three categories described device operation: controller, ATN (Attention)-The ATN line is an important manage-
talker, and listener. The controller regulates other devices ment line. ATN line status indicates if controller informa-
on the bus, the talker sends data, and the listener receives tion on the data bus is to be considered data (set high false)
data. A particular device may be a talker only or both a or a multiline command (set low).
talker and a listener. A system can have only one controller
(although control may be passed on to an appropriate IFC (Interface Clear)-The IFC line, set true (low), sends
device through a special command). Several talkers and the bus to a known state by sending the IFC command.
listeners may be present depending on the bus's
capabilities. REN (Remote Enable)-The REN line, set low, sets up in-
struments on the bus for remote operation.
The bus is limited to 15 devices including the controller. EOI (End or Identify)-The EOI line, set low, sends the
The maximum cable length is 20m. command to terminate a multi-byte transfer sequence.
SRQ (Service Request)-The SRQ line is set low by a device
Several devices may listen simultaneously, but only one when it requires service from the controller.
device at a time may be a talker. Otherwise, communica-
tion would be garbled.
2.3.2 Handshake Lines
Before a device can be a talker or a listener, it must be ap-
The bus uses three handshake lines that operate in an in-
propriately addressed. Devices are selected according to
terlocked sequence. This method ensures reliable data
their primary address; the addressed device is sent a talk
transfer regardless of the transfer rate. Generally, the
or listen command derived from its primary address. Each
slowest active device on the bus determines the data
device on the bus has a unique address so that each may
transfer rate.
be addressed individually.
Of the three bus handshake lines, the data source controls
Once a device is addressed to talk or listen, appropriate
one and the accepting device controls the other two. The
bus transactions take place. For example, if an instrument
handshake lines are:
is addressed to talk, it sends its data to the bus one byte
at a time. The listening device reads this information, and
DAV (Data Valid)-The source controls the state of the DAV
the appropriate software is then used to channel the in-
line.
formation to the desired location.
NRFD (Not Ready For Data)-The acceptor controls the
state of the NRFD line.
2.3 IEEE-488 BUS LINES
NDAC (Not Data Accepted)--The acceptor controls the state
Three types of signal lines are found on the IEEE-488 bus of the NDAC line.
lines: data lines, which handle bus information, and hand-
shake and bus management lines, which ensure proper
data transfer and bus operation. Each of these bus lines Figure 2-2 illustrates the complete handshake sequence for
is "active low" so that approximately zero (0) volts is a logic one data byte. Once data is on the bus, the source con-
one (1). The following paragraphs describe the purpose firms that NRFD is high, indicating that all devices on the
of these lines, which are illustrated in Figure 2-l. bus are ready for data. Simultaneously, NDAC is low from
the previous byte transfer. If these conditions are not met,
the source must wait until the NRFD and NDAC lines have
2.3.1 Bus Management Lines the correct status. If the source is a controller, NRFD and
NDAC must remain stable for at least 1OOnsec after ATN
is low. Some controllers have time-out routines to display
The bus management group includes five signal lines that
error messages if the handshake sequence stops for any
ensure orderly data transfer. These lines send the uniline
reason to reduce the possibility of bus hang-up.
commands described in paragraph 2.4.1.
2-2
AN OVERVIEW OF THE IEEE-488 BUS
DAV line high, indicating bus data is invalid, and the
NDAC line returns to its low state. Finally, each of the
devices releases the NRFD line at its own rate until it goes
DATA SOURCE
X high when the slowest device is ready. The bus is then set
to repeat the sequence with the next data byte.
DAV SOURCE
VALlD 2.3.3 DBtB Lines
I
I
MRFD ACCEPTOR
I The IEEE-488 bus uses eight data lines that allow data to
I I be transmitted and received in a bit-parallel, byte-serial
I 1
manner. The eight lines are labeled DIOl through DI08, are
I I
bidirectional and, as with the remaining bus signal lines,
I
I low is true.
NOAC I ACCEPTOR
I I
DAiA OAt A 2.4 BUS COMMANDS
TRANSFER TRANBFER
BE61N END This section briefly describes the purpose of the bus com-
mands that control communication between various in-
struments on the bus. The commands can be divided into
Figure 2-2. Handshake Sequence three categories.
Once the NRFD and NDAC lines are properly set, the Uniline Commands-Sent by setting the associated bus
source sets the DAV line low (data on the bus is now valid). line low.
The NRFD line then goes low, and the NDAC line goes
high after all devices on the bus have accepted the data. Multiline Commands-General bus commands which are
Each device releases the NDAC line at its own rate. The sent over the data lines with the ATN line low.
NDAC line will not go high until the slowest device has
accepted the data byte. Device-dependent Commands-Special commands that
depend on device configuration; sent over the data lines
with ATN high.
After the NDAC line goes high, the source then sets the
2-3
AN OVERVIEW OF THE IEEE-488 BUS
Table 2-1. IEEE-488 Bus Command Summary
-I-
State of
Command Type Command ATN Line* Comme"ts
Uniline REN (Remote Enable) X Set up for remote operation.
EOI (End Or Identify) X Sent by setting EOI'low
IFC (Interface Clear) i X Clear interface.
ATN (Attention) Low Defines data bus contents.
SRQ (Service Request) X Controlled by external device. -1
Multiline t
Universal DCL (Device Clear) Low Returns to default conditions.
WE (Serial Poll Enable) Low Enables serial polling.
SI'D (Serial Poll Disable) Low Disables serial polling.
Addressed SDC (Selective Device Clear) Low Returns unit to default conditions.
GTL (Go To Local) Low Returns to local control,
GET (Group Execute Trigger) Low Triggers device for reading.
Unaddressed UNL (Unlisten) Low Removes all listeners from bus.
UNT (Untalk) Low Removes all talkers from bus.
Device-dependent** High Commands for control of the
instrument.
*X = Don't Care
*`See paragraph 4.3 for complete description.
2.4.1 Uniline Commands SRQ (Service Request)-Asserted by an external device
when it requires service from the controller. A serial poll-
Uniline commands are sent by setting the associated bus ing sequence, as described in Section 4, must be used in
line low. The ATN, IFC and REN commands are asserted case of multiple devices to determine which device has re-
only by the system controller. The SRQ command is sent quested service.
by either the controller or an external device depending
on the direction of data transfer. The following is a brief
description of each command. 2.4.2 Universal Commands
Universal commands are multiline commands that require
ATN (Attention)-Controller sets ATN when transmitting no addressing. All inshumentation equipped to implement
addresses or multiline commands. Device-dependent com- the command will do so simultaneously when the com-
mands are sent with the ATN line high (false). mand is transmitted over the bus. The universal com-
mands, like all multiline commands, are sent over the data
IFC (Interface Clear)-Clears the bus and sets devices to line with ATN low.
a known state. Although device configurations differ, the
IFC command usually places instruments in the talk and
listen idle states. LLO (Local Lockout)-The LLO command is used to lock
out front panel controls on devices so equipped.
REN (Remote Enable)-Sets instrument up for remote
operation. The REN command should be sent before at- DCL (Device Clear)-After DCL is sent, instrumentation
tempting to program the instruments over the bus. equipped to implement the commands will revert to a
known state. Usually, instruments return to their power-
EOI (End or Identify)-Positively identifies the last byte up conditions.
in a multi-byte transfer sequence, and allows variable
length data words to be easily transmitted.
2-4
AN OVERVIEW OF THE IEEE-488 BUS
Sl'E (Serial Poll Enable)--The SPE command is the first step 2.4.4 Unaddressed Commands
in the serial polling sequence. The serial polling sequence
is used to determine which instrument has requested ser- The controller uses two unaddressed commands to
vice with the SRQ command. simultaneously remove all talkers and listeners from the
bus. ATN is low when these multiline commands are
SPD (Serial Poll Disable)-The SPD command is sent by asserted.
the controller to remove all instrumentation from the serial
.poll mode.
UNL (Unlisten)-All listeners are immediately removed
from the bus when the UNL command is placed on the
2.4.3 Addressed Commands bus.
Addressed commands are multiline commands that must UNT (Untalk)-The controller sends the UNT command
be preceded by a listen command before the instrument to clear the bus of all talkers.
will respond. The listen command is derived from the
device's primary address. Only the addressed device will
respond to the following commands: 2.4.5 Device-Dependent Commands
The instrument determines device-dependent command
SDC (Selective Device Clear)-The SDC command is definition. Generally, these commands are sent as ASCII
essentially identical to the DCL command except that on- characters that tell the device to perform a specific func-
ly the addressed device responds. The addressed instru- tion. For example, Zl places the instrument in the relative
ment usually returns to its default conditions when SDC mode. For complete information on using these commands
is sent. with the Model 5802, refer to Section 4. The IEEE-488 bus
treats device-dependent commands as data with the ATN
GTL (Go To Local)-The GTL command removes in- line high (false) when the commands are transmitted.
struments from the remote operation mode. Also, front
panel operation will usually be restored if LLO was already
sent.
2.5 COMMAND CODES
GET (Group Execute Trigger)-The GET command is used
to trigger devices to perform a device-dependent action. Each multiline command has a unique code that is
Although GET is considered an addressed command, transmitted over the bus as 7 bit ASCII data. This section
many devices respond to GET without being addressed. briefly explains the code groups which are summarized
in Figure 2-3. Every command is sent with ATN true.
2-5
AN OVERVIEW OF THE IEEE-466 BUS
Figure 2-3. Command Codes
2-6
AN OVERVIEW OF THE IEEE-466 BUS
Addressed Command Group (ACG)-Address commands Table 2-2. Hexadecimal and Decimal Command
are listed in column O(8) in Figure 2-3. Column O(A) lists Codes
the corresponding ASCII codes.
Universal Command Group (UCG)-Columns l(A) and Command Hex Value'
l-
Decimal Value
l(B) list universal commands and the corresponding ASCII
codes.
GTL 01
Listen Address Group (LAG)-Columns 2(A) and 3(A) list SDC 04 i
the ASCII codes corresponding to the primaly addresses GET 08 8
listed in columns 2(B) and 3(B). For example, if the primary DCL 14 20
address is set to l2, the LAG byte will correspond to an WE 18 24
ASCII(,) command. SPD 19 25
LAG 20-3F 32-63
Talk Address Group (TAG)--TAG primary address values TAG 40-5F 64-95
and the corresponding ASCII characters are listed in col-
UNL 3F 63
umns 4(A) through 5(B).
UNT 5F 95
The preceding address groups are combined to form the *Values shown with D7 = 0
Primary Command Group (KG). The bus also has
another group of commands, the Secondary Command
Group (SCG). These are listed in Figure 2-3 for reference 2.6 COMMAND SEQUENCES
only; the Model 5802 does not respond to these com-
mands, although other devices may have secondary ad-
The proper command sequence must be sent by the con-
dressing capability.
troller before an instrument will respond as intended. The
universal commands such as LLO and DCL require only
that ATN be set low before the command is sent. Other
NOTE
commands require that the device be addressed to listen
Commands are normally transmitted with the 7
first. This section briefly describes the bus sequence for
bit code listed in Figure 2-3. The condition of D7
several types of commands.
(D108) is usually uni◦ Jabse Service Manual Search 2024 ◦ Jabse Pravopis ◦ onTap.bg ◦ Other service manual resources online : Fixya ◦ eServiceinfo