Tektronix 5802 Instruction Manual

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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 original 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, INDIRECT, 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

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 using this product and any associated instrumentation. Although sane instruments and accessories would normally be used with non-hazardous voltages, there are situations where hazardous conditions may be present.

This product is intended for use by qualified personnel who recognize shock hazards and are familiar with the safety pre-

cautions required to avoid possible injury. Read the operating

information carefully before using the product.

Exercise extreme caution when a shock hazard is present. Lethal voltage may be present on cable connector jacks or test fixtures. The American National Standards Institute (ANSI) states that a shock hazard exists when voltage levels greater than 3OV RMS, 42.4V peak, or 60VDC are present. A good safety practice is to expect that hazardous voltage is present in any unknown circuit before measuring.

Before operating an instrument, make sure the line cord is connected to a properly grounded power receptacle. Inspect the connecting cables, test leads, and jumpers for possible wear, cracks, or breaks beforr each use.

For maximum safety, do not touch the product, test cables, or any other instruments while power is applied to the circuit under test. ALWAYS remove power from the entire test system and discharge any capacitors before: connecting or disconnecting cables or jumpers, installing or removing switching cards, or making internal changes, such as installing or removing jumpers.

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

while standing on a dry, insulated surface capable of with-

standing the voltage being measured.

Do not exceed the maximum signal levels of the instruments and accessories, as defined in the specifications and operating information, and as shown on the instrument or test fixture rear panel, or switching card.

Do not connect switching cards directly to unlimited power circuits. They are intended to be used with impedance limited sources. NEVER connect switching cards directly to AC main. When connecting sources to switching cards, install protective devices to limit fault current and voltage to the card.

When fuses are used in a product, replace with same type and rating for continued protection against fire hazard.

Chassis connections must only be used as shield connections for measuring circuits, NOT as safety earth ground connections.

If you are using a test fixture, keep the lid closed while power is applied to the device under test. Safe operation requires the use of a lid interlock.

If a @screw is present on the test fixture, connect it to safety earth ground using #18 AWG or larger wire.

The $ symbol on an instrument or accessory indicates that 1OOOV or more may be present on the terminals. Refer to the product manual for detailed operating information.

Instrumentation and accessories should not be connected to humans.

Maintenance should be performed by qualified service personnel. Before performing any maintenance, disconnect the line cord and all test cables.

SPECIFICATIONS/5802

ANALOG OUTPUT LEVEL: 1” = 10,cal CO”“tS 0” Xl gain.

1” = 100 Counts on Xl00 gain,

Maximurn output voltage = *‘iv.

ACC”RACY: *(0.25% 0, displayed reading +*r”“)~ In x100. 2mV

output = 0.2 displayed aunts.

:EEE-488 BUS IMPLEMENTATION

RESPONSE TIME: FdlOWS d,splay cnnversion rate,

OUTPUT RESISTANCE: 1OOOn~ ISOLATION: ANALOC; OUTPUT LO is connected to ,EEE COM-

MON. Maximum cwnmo” mode voltage from IEEE COMMON to

earth ground is 3W rms al dc. 50 or 6011~~

.l”l.T,LINE COMMANDS: DCL. SK, GET. GTL. UNT. UNL.

WE. 3’“. LLO,

lN,L,NE COMMANDS: IFC, EN, EOI, SRQ, ATN,

NTERFACE FUNCTIONS: SHl. AH,. T5, TEO. L4. LEO, SRI. RLO.

PPO. DC,, DT,, CU. El.

‘ROCRAMMABLE PARAMETERS: Range. DRY CIRCUIT

TEST,Operate, RELative. POLARITY, DRIVE. TRlCger. Calibra-

tian. EOI, SRQ. Status. Data Format. Terminatar~

,E”,CE-DEPENDENT COMMANDS:

RANGE:

;: R-3 20 n 114 200 n R5 2k n Rb 2Ok n R7 200k n

RELATIVE:

ZO = REL ofi Z, = REL on

OPERATE:

0” = STBY (Standby1 0, = OPR (Operatv)

POLARITY:

PO = FOL + Pi = I’OL -

DRIVE:

DO = DRIVE (puked) D, = DRIVE

DRY ClRCUIT TEST:

CO = NON DRY CIRCUIT TEST C, = DRY CIRCUIT TEST

D,G,TAL CALIBRATION:

v * n.nn,,,,~ * nn = enter calibratiun value.

STORE:

LO = Store calibration constants.

NON

DRY CIRCUIT

TEST

A”to

2”“rnII

2 R

(dc)

DRY CIRCUIT

TEST

Auto

2OOmll

2 0 20 0 20 0 20 n 20 0 20 0

TRIGGER:

TO = Continuous on Talk T, = One-shot on Talk T2 = Continuous ~1” GET T3 = O”e~shr,t <>n GET T4 = Cantinuous on X TZ = One-shut on X

EXECUTE:

X = Exerute drviwdcprndent cwnmands

EO,:

KO = EOI Enabled K1 = EO, “isabied

STATUS WORD:

ti” = Ourput status word,

DATA FORMAT:

GO = Readings and status word with preiix C, = Readings and status word withut pretix

SRQ:

MO = Clear SRQ Data Mask MI = Reading Overthn% MS i Reading D”“r M9 = Reading Done or Reading Ovcrfh

Ml6 = BUS)

M,, = Busy ,,T Reading Overflw M24 = Busy or Reading Dane M25 = Busy. Reading hne i)r Reading Overflw M32 = Clear SRQ Ermr Mask M33 = IDDCO M34 = IDDC M3S = ,DDC or IDDCO M36 = Not in Remote ,437 = Not in Remok or ,DDCCl

M3X = Not in Rem<>tr or ,D,,C

M39 = Not in Remote. lDDC or (“DC0

TERMINATOR:

Y(ASC,I) = ASCII Character

Y(LF) = CR LF Y(CR) = LF CR Y(DEL, = None

T,ME FROM TRlGGER TO FlRST BYTE OUT: 350”~s 10 500ms.

ADDRESS MODES: Taik Only. Addressable

DATA FORMAT AND STATUS BYTE OUTPUT

DATA FORMAT: STATUS BY-I-E OUTPUT:

TERMINATOR I

EXPONENT

PREF’X -FL u-l

N + DP + I.23456 E + 2 ,cR)(LF,

(pulsed)

D = DRIVE S=STANDBY J L N = NORMAL O=OVERFLOW D=DRY

Z = RELATIVE CIRCUIT TEST

DRY CIRCUIT TEST: N = NON DRY

POLARITY: + = POL +

- =POL -

id4

CIRCUIT TEST

580 D P C 0 R Z K T Md Me H Y

RELATIVE

TRIGGER

SRQ ON DATA

SRQ ON ERROR

LINE FREQUENCY A

TERMINATOR

PREFIX DRIVE POLARITY

DRY CIRCUIT TEST OPERATE RANGE

EOI

TABLE OF

SECTION l-GENERAL INFORMATION

CONTENTS

1.1

1.2

1.3

1.4

1.5

1.6 USING THE INSTRUCTION MANUAL

1.7

1.8 UNPACKING AND INSPECTION..

INTRODUCTION INTERFACE FEATURES WARRANlY INFORMATION MANUAL ADDENDA SAFETY SYMBOLS AND TERMS

SPECIFICATIONS

......

SECTION 2-AN OVERVIEW OF THE IEEE-488 BUS

2.1 INTRODUCTION

2.2

2.3 IEEE-488 BUS LINES

2.3.1 BusManagement Lines

2.3.2 Handshake Lines

2.3.3 Data Lines

2.4 BUS COMMANDS

2.4.1

2.4.2

2.4.3 Addressed Commands

2.4.4 Unaddressed Commands

2.4.5 Device-Dependent Commands

2.5

2.6 COMMAND SEQUENCES

2.6.1 Addressed Command Sequence

2.6.2

2.6.3 Device-Dependent Command Sequence ......................................................

BUS DESCRIPTION

UniIine Commands Universal Commands

COMMAND CODES

Universal Command Sequence

............................................................................

..........................................................................

.........................................................................

.....................................................................

...........................................................................

.................................................................................

...........................................................................

.........................................................................

.......................................................................

......................................................................

...................................................................

..............................................................

.........................................................................

...................................................................

............................................................. 2-7

..............................................................

......

..,...

1-l 1-l 1-l 1-l 1-l 1-l l-2

l-2

2.1 2-l 2-2 2-2 2-2 2-3

2.3 2-4 2-4

2-5 2-5 2-5

2.5 2-7

2-8 2-8

SECTION 3-SYSTEM CONFIGURATION

3.1 INTRODUCTION

3.2 HARDWARE CONSIDERATIONS .............................................................

3.2.1 Typical Systems

3.2.2 Bus Connections

3.2.3 Primary Address Selection..

3.3

3.3.1 Controller Interface Routines

3.3.2 HP-85BASIC Statements

3.3.3 InterfaceFunction Codes ....................................................................

3.3.4 Interface Commands

SOFTWARE CONSIDERATIONS .............................................................

............................................................................

...........................................................................

................................................................

...................................................................

.......................................................................

3-l 3-l 3-l 3-2

3-4 3-5

3-5 3-5

3-6 3-7

SECTION 4-OPERATION

4.1

4.2

4.2.1

4.2.2

4.2.3 i.2.4

4.2.5

4.2.6

4.2.7

4.3

4.3.1

4.3.2

4.3.3

4.3.4

4.3.5

4.3.6

4.3.7

4.3.8

4.3.9

4.3.10

4.3.11

4.3.12

4.3.13

4.3.14

4.3.15

4.4

INTRODUCTION ..............

GENERAL BUS COMMANDS

REN (Remote Enable). ........

IFC (Interface Clear) ..........

GTL (Go To Local) ...........

LLO (Local Lockout). .........

DCL (Device Clear). ..........

SDC (Selective De&ce Clear) Serial Polling (SPE, SPD)

DEVICE-DEPENDENT COMMAND PROGRAMMING..

Execute(X) ..........................

Range (R) ...........................

Operate/Standby (0) .................

Dry Circuit Test (C) ..................

Relative (2). .........................

Digital Calibration (V) and Storage (L)

Polarity (P) ..........................

Drive (D) ............................

Triggering (T) ............................

EOI (K) .................................

SRQ Mode (M) and Status Byte Format ....

Status Word (U) or Alternate Output ......

Prefix(G)

Programmable Terminator (Y) .............................................................. 4-14

Data Format .............................................................................. 4.14

TALK ONLY OPERATION ..................................................................

.................................................................................

.......

......

..........

.................................................

................................................

......

4-l 4-l 4-l 4-2 4-2 4-2 4-3 4-3 4-3 4-4

4-b

4-6 4-6 4-6 4-7 4-7 4-8 4-8 4-8 4-8

4-9 4-13 4-13

4.15

SECTION 5-ANALOG OUTPUT

5.1

5.2

5.3

5.4

INTRODUCTION ............................................................................

USING THE ANALOG OUTPUT .............................................................

OUTI’UTRESISTANCE ......................................................................

Xl00 RESOLUTION AND ACCURACY

........................................................

SECTION 8-PRINCIPLES OF OPERATION

6.1

6.2

6.2.1

6.2.2 Digital Circuitry..

6.2.3

INTRODUCTION ............................................................................

CIRCUIT DESCRIPTION .....................................................................

Power Supply .............................................................................

..........................................................................

Analog Output .............................................................................

SECTION 7-MAINTENANCE

7.1

7.2

7.3

7.3.1

7.3.2

7.3.3

7.3.4 Calibration. ................................................................................

7.4 SPECIAL HANDLING OF STATIC-SENSITIVE DEVICES

7.5 TROUBLESHOOTING

INTRODUCTION ............................................................................

INSTALLATION .............................................................................

CALIBRATION ..............................................................................

Warm Up .................................................................................

Recommended Calibration Equipment ........................................................

Environmental Conditions ..................................................................

.......................................................................

.......................................

5-l

5-3

b-1

6-l

6-2

7-l

7-3

SECTION 8--REPLACEABLE PARTS

8.1

8.2

8.3

8.4

8.5

INTRODUCTION ............................................................................

REPLACEABLE PARTS. ORDERING INFORMATION FACTORY SERVICE SCHEMATIC DIAGRAMS AND COMPONENT LOCATION DRAWINGS

......................................................................

.................................................................

.........................................................................

8-l 8-l 8-1 8-l

........................ 8-1

iii

LIST OF TABLES

SECTION 2-AN OVERVIEW OF THE IEEE-488 BUS

2-l 2-2 2-3 2-4

IEEE-488 Bus Command Summary .,,,...,,.._...,,,.,..,,,._..................,,............. 2-4

Hexadecimal and Decimal Command Codes.. 2-7 Typical Addressed Command Sequence.. 2-8 Typical Device-Dependent Command Sequence 2-8

SECTION 3-SYSTEM CONFIGURATION

3-l 3-2 3-3 3-4 3-5

IEEE-488 Contact Designations Primary Address Switch Positions HP-85 IEEE-488 BASIC Statement Interface Function Codes IEEE-488 Command Groups

................................................................

.............................................................

.......................................................

..................................................................

SECTION 4-OPERATION

4-l 4-2 4-3 4-4 4-5 4-6

GeneralBus Commands Default Values (Status Upon Power Up or After SDC or DCL). Device-Dependent Command Summary RangeCommands SRQMask Commands Status Byte and Mask Interpretation

......................................................................

........................................................

...........................................................................

.......................................................................

..........................................................

SECTION t&ANALOG OUTPUT

5-l AnalogOutputParameters....................................................................

..................................

.............

3-3 3-4

3-6 3-7 3-7

4-l 4-4

4-5 4-6 4-9

4-10

5-3

SECTION 7--MAINTENANCE

7-1 Static SensitiveDevices.......................................................................

7-2 Model5802InterfaceChecks..................................................................

SECTION 8-REPLACEABLE PARTS

8-l

Model5802Parts List _...._.........................._.,.,.___.,...._.._.__._................ 8-2

7-3 7-4

LIST OF ILLUSTRATIONS

SECTION 2-AN OVERVIEW OF THE IEEE-488 BUS

2-l 2-2 2-3

IEEE-488 Bus Configuration ...... .. ......................... ..................... 2-l

Handshake Sequence

Command Codes ............ _......

.........................................................................

SECTION 3-SYSTEM CONFIGURATION

3-l SystemTypes 3-2 IEEE-488 Connector 3-3 IEEE-488 Connections 3-4 3-5 3-6 3-7

Contact Assignments Rear Panel of Model 580 Showing IEEE-488 Connections and Switches Typical IEEE-488 Bus Drive (one of 16). Primary Address Switch (Address 25 Shown)

......................................................

.................................................

...............................................

................................................

SECTION 4-OPERATION

4-l Status Byte Format 4-2 4-3

General Format for UO Command Data Format

..........................................................................

............................................................

................................................................................

SECTION 5-ANALOG OUTPUT

5-l 5-2 5-3

Analog Output Connections

Xl Analog Output ........................................................................... 5-2

XlOOAnalog Output .._ ...................................................................... 5-3

..................................................................

........................................................

...............................

.........................

2-3 2-6

3-l 3-2 3-2 3-2 3-3 3-3 3-4

4-10 4-11 4-14

5-l

SECTION 6-PRINCIPLES OF OPERATION

6-l 6-2 6-3

Simplified Block Diagram.. ................................................................... 6-l

Memory Map

Xland Xl00 Gains ........................................................................... 6-3

................................................................................

SECTION 7-MAINTENANCE

7-l

Model 5802 Installation

.......................................................................

SECTION 8-REPLACEABLE PARTS

8-l

8-2

Model 5802 Interface, Component Location Drawing, Dwg. No. 5802-100 Model 5802 Interface, Schematic Diagram, Dwg. No. 5802-106

6-2

7-2

......................... 8-4

................................... 8-5

SECTION 1

GENERAL INFORMATION

1.1 INTRODUCTION

The Model 5802 is an IEEE-488 interface for the Model 580 Micro-ohmmeter. This interface, which includes analog output, adds extra versatility to the Model 580 by allowing the transmission of data and commands over the IEEE-488 bus. The interface provides all the necessary logic to interface the Model 580 to the bus using standard IEEE-488-1978 protocol.

1.2 INTERFACE FEATURES

Important IEEE-488 interface features:

l With the Model 5802 installed, the Model 580 is able to

communicate with other insrmmentation using the same IEEE-488s1!778 standards.

l A standard IEEE-488 connector that provides easy con-

nection to the IEEE-488 bus.

l An easily-changeable primary address. Although the

Model 580 is shipped from the factory with a primary address of 25, the customer can change it by using the five rear panel address switches.

l All Model 580 operation is supported by IEEE-488 pro-

gramming. In addition, numerous other IEEE-488 commands add operating features not available from the front pSW1.

1.4 MANUAL ADDENDA

Information concerning improvements or changes to the instrument which occur after the printing of this manual may be found on an addendum included with this manual. Review these changes before programming the Instrument.

1.5 SAFETY SYMBOLS AND TERMS

The following safety symbols and terms are used in this manual and may be found on the instrument.

The A symbol on the instrument indicates that the user should refer to the operating instructions.

Information associated with the WARNING heading explains dangers that could result in personal injury or death.

Information following the CAUTION heading explains hazards that could damage the instrument.

1.6 USING THE INSTRUCTION MANUAL

1.3 WARRANTY INFORMATION

Warranty information may be found on the inside front cover of this manual. Should it become necessary to exercise the warranty, contact your Keithley representative or the factory to determine the proper course of action. Keithley Instruments, Inc. maintains service facilities in the United States, the United Kingdom and throughout Europe. Addresses for these facilities may be found inside the front cover of this manual. Information concerning the application, operation or service of your instrument may be directed to the applications engineer at any of these locations.

This manual contains all the information you need to con- nect the Model 5802 to the IEEE-488 bus and program the instrument from a separate bus controller.

The manual is divided into the following sections:

1. Section 2 contains a general description of the IEEE-488 bus and its commands.

2. Section 3 contains information necessary to connect the instrument to the bus and set the primary address.

3. Section 4 contains the bulk of the programming information. 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 Model 5802.

5. Section 6 contains Principles of Operation.

6. Section 7 contains maintenance information such as installation and troubleshooting.

7. Section 8 contains replaceable parts information and applicable schematics and component layouts.

and electrically before shipment. When the Model 5802 arrives, carefully unpack all items and check for any obvious signs of damage.

Report any damage to the shipping agent immediately. Retain and use the original packing material in case reshipment is necessary. The following items are shipped with every Model 5802 order:

1.7 SPECIFICATIONS

A complete list of IEEE-488 specifications can be found preceding this section.

1.8 UNPACKING AND INSPECTION

The Model 5802 was carefully inspected both mechanically

Model 5802 IEEE-488 Interface Hardware necessary for installation

Model 5802 Instruction Manual

Additional accessories as ordered

If you need another manual, order the manual package

(Keithley Part No. 5802-901-01). This package includes an

instruction manual and any pertinent addenda.

l-2

2.1 INTRODUCTION

SECTION 2

AN OVERVIEW OF THE IEEE-488 BUS

The IEEE-488 bus is an instrumentation data bus adopted by the IEEE (Institute of Elechical and Eleckonic Engineers) in 1975 and given the IEEE-488 designation. The most recent 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 description of a complicated set of standards. Rather, this section briefly describes general bus structure including a bus command outline. Complete IEEE-488 bus information is available from the IEEE and other sources.

2.2 BUS DESCRIPTION

The IEEE-488 bus is a parallel data transfer medium that 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.

TO OTHER DEVlCES

/ * \

DATA BYTE

TRANSFER

CONTROL

INTERFACE

HANDSHAKE

A typical bus configuration for controlled operation is

shown in Figure 2-l. A typical system has one controller and one or more instruments that receive commands and

which usually yield data.

BUS

MANAGEMENT

Figure 2-1. IEEE-488 Bus Configuration

2-1

AN OVERVIEW OF THE IEEE-488 BUS

Three categories described device operation: controller, talker, and listener. The controller regulates other devices on the bus, the talker sends data, and the listener receives data. A particular device may be a talker only or both a talker and a listener. A system can have only one controller (although control may be passed on to an appropriate device through a special command). Several talkers and listeners may be present depending on the bus’s capabilities.

The bus is limited to 15 devices including the controller. The maximum cable length is 20m.

Several devices may listen simultaneously, but only one device at a time may be a talker. Otherwise, communication would be garbled.

Before a device can be a talker or a listener, it must be appropriately addressed. Devices are selected according to their primary address; the addressed device is sent a talk or listen command derived from its primary address. Each device on the bus has a unique address so that each may be addressed individually.

ATN (Attention)-The ATN line is an important management line. ATN line status indicates if controller information on the data bus is to be considered data (set high false) or a multiline command (set low).

IFC (Interface Clear)-The IFC line, set true (low), sends the bus to a known state by sending the IFC command.

REN (Remote Enable)-The REN line, set low, sets up in- struments on the bus for remote operation.

EOI (End or Identify)-The EOI line, set low, sends the command to terminate a multi-byte transfer sequence.

SRQ (Service Request)-The SRQ line is set low by a device when it requires service from the controller.

2.3.2 Handshake Lines

The bus uses three handshake lines that operate in an interlocked sequence. This method ensures reliable data transfer regardless of the transfer rate. Generally, the slowest active device on the bus determines the data transfer rate.

Once a device is addressed to talk or listen, appropriate bus transactions take place. For example, if an instrument is addressed to talk, it sends its data to the bus one byte at a time. The listening device reads this information, and the appropriate software is then used to channel the information to the desired location.

2.3 IEEE-488 BUS LINES

Three types of signal lines are found on the IEEE-488 bus lines: data lines, which handle bus information, and handshake and bus management lines, which ensure proper data transfer and bus operation. Each of these bus lines is “active low” so that approximately zero (0) volts is a logic one (1). The following paragraphs describe the purpose of these lines, which are illustrated in Figure 2-l.

2.3.1 Bus Management Lines

The bus management group includes five signal lines that ensure orderly data transfer. These lines send the uniline commands described in paragraph 2.4.1.

Of the three bus handshake lines, the data source controls one and the accepting device controls the other two. The handshake lines are:

DAV (Data Valid)-The source controls the state of the DAV line.

NRFD (Not Ready For Data)-The acceptor controls the state of the NRFD line.

NDAC (Not Data Accepted)--The acceptor controls the state of the NDAC line.

Figure 2-2 illustrates the complete handshake sequence for one data byte. Once data is on the bus, the source confirms that NRFD is high, indicating that all devices on the 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 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 error messages if the handshake sequence stops for any reason to reduce the possibility of bus hang-up.

2-2

DATA

DAV

SOURCE

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 high when the slowest device is ready. The bus is then set

to repeat the sequence with the next data byte.

MRFD

NOAC

VALlD

I I I I I I I I

DAiA

TRANSFER

BE61N

1 I

OAt A

TRANBFER

END

ACCEPTOR

Figure 2-2. Handshake Sequence

Once the NRFD and NDAC lines are properly set, the source sets the DAV line low (data on the bus is now valid). The NRFD line then goes low, and the NDAC line goes high after all devices on the bus have accepted the data. Each device releases the NDAC line at its own rate. The NDAC line will not go high until the slowest device has accepted the data byte.

After the NDAC line goes high, the source then sets the

2.3.3 DBtB Lines

The IEEE-488 bus uses eight data lines that allow data to be transmitted and received in a bit-parallel, byte-serial manner. The eight lines are labeled DIOl through DI08, are bidirectional and, as with the remaining bus signal lines, low is true.

2.4 BUS COMMANDS

This section briefly describes the purpose of the bus commands that control communication between various instruments on the bus. The commands can be divided into

three categories.

Uniline Commands-Sent by setting the associated bus line low.

Multiline Commands-General bus commands which are sent over the data lines with the ATN line low.

Device-dependent Commands-Special commands that

depend on device configuration; sent over the data lines

with ATN high.

2-3

AN OVERVIEW OF THE IEEE-488 BUS

Table 2-1. IEEE-488 Bus Command Summary

-I-

Command Type

Uniline

Command

REN (Remote Enable)

EOI (End Or Identify) IFC (Interface Clear) ATN (Attention) SRQ (Service Request)

Multiline

Universal

DCL (Device Clear) WE (Serial Poll Enable) SI’D (Serial Poll Disable)

Addressed

SDC (Selective Device Clear) GTL (Go To Local) GET (Group Execute Trigger)

Unaddressed

UNL (Unlisten)

UNT (Untalk)

Device-dependent**

*X = Don’t Care

*‘See paragraph 4.3 for complete description.

State of

ATN Line*

X X

Low

Low Low Low Low Low Low Low Low

High

Comme”ts

Set up for remote operation. Sent by setting EOI’low Clear interface. Defines data bus contents. Controlled by external device.

Returns to default conditions. Enables serial polling. Disables serial polling. Returns unit to default conditions. Returns to local control,

Triggers device for reading.

Removes all listeners from bus. Removes all talkers from bus.

Commands for control of the

instrument.

-1

2.4.1 Uniline Commands

Uniline commands are sent by setting the associated bus line low. The ATN, IFC and REN commands are asserted only by the system controller. The SRQ command is sent by either the controller or an external device depending on the direction of data transfer. The following is a brief description of each command.

ATN (Attention)-Controller sets ATN when transmitting addresses or multiline commands. Device-dependent commands are sent with the ATN line high (false).

IFC (Interface Clear)-Clears the bus and sets devices to

a known state. Although device configurations differ, the

IFC command usually places instruments in the talk and

listen idle states.

REN (Remote Enable)-Sets instrument up for remote operation. The REN command should be sent before attempting to program the instruments over the bus.

EOI (End or Identify)-Positively identifies the last byte in a multi-byte transfer sequence, and allows variable length data words to be easily transmitted.

SRQ (Service Request)-Asserted by an external device when it requires service from the controller. A serial polling sequence, as described in Section 4, must be used in case of multiple devices to determine which device has requested service.

2.4.2 Universal Commands

Universal commands are multiline commands that require no addressing. All inshumentation equipped to implement the command will do so simultaneously when the command is transmitted over the bus. The universal commands, like all multiline commands, are sent over the data line with ATN low.

LLO (Local Lockout)-The LLO command is used to lock out front panel controls on devices so equipped.

DCL (Device Clear)-After DCL is sent, instrumentation equipped to implement the commands will revert to a known state. Usually, instruments return to their powerup conditions.

2-4

AN OVERVIEW OF THE IEEE-488 BUS

Sl’E (Serial Poll Enable)--The SPE command is the first step in the serial polling sequence. The serial polling sequence is used to determine which instrument has requested ser-

vice with the SRQ command.

SPD (Serial Poll Disable)-The SPD command is sent by the controller to remove all instrumentation from the serial

.poll mode.

2.4.3 Addressed Commands

Addressed commands are multiline commands that must be preceded by a listen command before the instrument will respond. The listen command is derived from the device’s primary address. Only the addressed device will respond to the following commands:

SDC (Selective Device Clear)-The SDC command is essentially identical to the DCL command except that only the addressed device responds. The addressed instrument usually returns to its default conditions when SDC is sent.

GTL (Go To Local)-The GTL command removes instruments from the remote operation mode. Also, front panel operation will usually be restored if LLO was already sent.

GET (Group Execute Trigger)-The GET command is used to trigger devices to perform a device-dependent action. Although GET is considered an addressed command, many devices respond to GET without being addressed.

2.4.4 Unaddressed Commands

The controller uses two unaddressed commands to

simultaneously remove all talkers and listeners from the bus. ATN is low when these multiline commands are asserted.

UNL (Unlisten)-All listeners are immediately removed from the bus when the UNL command is placed on the bus.

UNT (Untalk)-The controller sends the UNT command to clear the bus of all talkers.

2.4.5 Device-Dependent Commands

The instrument determines device-dependent command definition. Generally, these commands are sent as ASCII characters that tell the device to perform a specific func-

tion. For example, Zl places the instrument in the relative mode. For complete information on using these commands with the Model 5802, refer to Section 4. The IEEE-488 bus treats device-dependent commands as data with the ATN line high (false) when the commands are transmitted.

2.5 COMMAND CODES

Each multiline command has a unique code that is

transmitted over the bus as 7 bit ASCII data. This section

briefly explains the code groups which are summarized

in Figure 2-3. Every command is sent with ATN true.

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Tektronix 5802 Instruction Manual

Specifications and Main Features

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