Measurement Digital488 User Manual

Digital488

INSTRUCTION MANUAL

IEEE 488 to Digital Interface

IOtech, Inc. • 25971 Cannon Road • Cleveland, Ohio 44146 • [phone]

Warranty Information

Your IOtech warranty is as stated on the product warranty card. You may contact IOtech by phone,
fax machine, or e-mail in regard to warranty-related issues.
Phone: [phone], fax: [phone], e-mail: [e-mail]

Limitation of Liability

IOtech, Inc. cannot be held liable for any damages resulting from the use or misuse of this product.

Copyright, Trademark, and Licensing Notice

All IOtech documentation, software, and hardware are copyright with all rights reserved. No part of this product may be copied, reproduced or transmitted by any
mechanical, photographic, electronic, or other method without IOtech’s prior written consent. IOtech product names are trademarked; other product names, as applicable, are
trademarks of their respective holders. All supplied IOtech software (including miscellaneous support files, drivers, and sample programs) may only be used on one
installation. You may make archival backup copies.

FCC Statement

IOtech devices emit radio frequency energy in levels compliant with Federal Communications Commission rules (Part 15)
for Class A devices. If necessary, refer to the FCC booklet How To Identify and Resolve Radio-TV Interference Problems
(stock # 004-000-00345-4) which is available from the U.S. Government Printing Office, Washington, D.C. 20402.

CE Notice

Many IOtech products carry the CE marker indicating they comply with the safety and emissions standards of the
European Community. As applicable, we ship these products with a Declaration of Conformity stating which
specifications and operating conditions apply.

Warnings, Cautions, Notes, and Tips

Refer all service to qualified personnel. This caution symbol warns of possible personal injury or equipment damage
under noted conditions. Follow all safety standards of professional practice and the recommendations in this manual.
Using this equipment i n ways other than described in t his manual can present serious safety hazards or cause equipment
damage.

This ESD caution symbol urges proper handling of equipment or components sensitive to damage from electrostatic
discharge. Proper handling guidelines include the use of grounded anti-static mats and wrist straps, ESD-protective
bags and cartons, and related procedures.

Specifications and Calibration

Specifications are subject to change without notice. Significant changes will be addressed in an addendum or revision to the manual. As applicable, IOtech calibrates its
hardware to published specifications. Periodic hardware calibration is not covered under the warranty and must be performed by qualified personnel as specified in this
manual. Improper calibration procedures may void the warranty.

Quality Notice

IOtech has maintained ISO 9001 certification since 1996. Prior to shipment, we thoroughly test our products and
review our documentation to assure the highest quality in all aspects. In a spirit of continuous improvement, IOtech
welcomes your suggestions.

Digital488

and

Digital488OEM

Instruction Manual

110-0920

Revision 4.2

November 1990

IOtech, Inc

.

●

25971 Cannon Road ● Cleveland, Ohio 44146 ● (440) 439-4 091

Table of Contents

Section1 Introduction Page

1.1 General Description 1.1

1.2 Available Accessories1.2

1.3 Specifications 1.3

1.4 Abbreviations 1.5

Section 2 Getting Started Page

2.1 Inspection 2.1

2.2 Configuration 2.1

2.2.1 IEEE Address Selection 2.2

2.2.2 IEEE Bus Output Terminator Selection 2.3

2.3 Digital Input/Output Ports 2.4

2.3.1 Logic Levels 2.4

2.3.2 Digital I/O Port Pin Outs 2.4

2.3.3 Control Lines 2.6

2.3.3.1 Clear 2.6

2.3.3.2 Data Strobe 2.7

2.3.3.3 External Data Ready 2.7

2.3.3.4 Inhibit 2.8

2.3.3.5 Trigger 2.9

2.3.3.6 Service 2.9

2.4 IEEE 488 Bus Implementation 2.9

2.4.1 My Talk Address (MTA) 2.10

2.4.2 My Listen Address (MLA) 2.11

2.4.3 Device Clear (DCL and SDC) 2.11

2.4.4 Group Execute Trigger (GET) 2.11

2.4.5 Interface Clear (IFC) 2.12

2.4.6 Serial Poll Enable (SPE) 2.12

2.4.7 Serial Poll Disable (SPD) 2.12

2.4.8 Unlisten (UNL) 2.12

2.4.9 Untalk (UNT) 2.12

2.5 Installation 2.13

Section 3 Command Descriptions Page

Introduction
Bit Set (An) 3.2
Bit Clear (Bn) 3.3
Bus Input/Output (Gn) 3.4

3.1

Table of Contents

Section 3 Command Descriptions Page

Section 4 IEEE 488 Primer Page

4.1 History 4.1

4.2 General St ructure 4.1

4.3 Send It To My Address 4.4

4.4 Bus Management Lines 4.4

4.4.1 Attention (ATN) 4.4

4.4.2 Interface Clear (IFC) 4.5

4.4.3 Remote Enable (REN) 4.5

4.4.4 End Or Identify (EOI) 4.5

4.4.5 Service Request (SRQ) 4.5

4.5 Handshake Lines 4.6

4.5.1 Data Valid (DAV) 4.6

4.5.2 Not Ready For Data (NRFD) 4.6

4.5.3 Not Data Accepted (NDAC) 4.6

4.6 Data Li nes 4.7

4.7 Multiline Commands 4.7

4.7.1 Go To Local (GTL) 4.7

4.7.2 Listen Address Group (LAG) 4.8

4.7.3 Unlisten (UNL) 4.8

4.7.4 Talk Address Group (TAG) 4.8

4.7.5 Untalk (UNT) 4.8

Configure (Cn) 3.5
Data (D...Z) 3.6
Data Ready (Rn) 3.8
End or Identify (Kn) 3.9
Execute (X) 3.10
Format (Fn) 3.11
Handshake (Hn) 3.18
Inhibit (Qn) 3.19
Invert (In) 3.20
Port (Pn) 3.21
Service Request Mask (Mn) 3.22
Serial Poll Status Byte 3.24
Status (Un) 3.26
Terminator (Yn) 3.29
Test (T0) 3.30

Table of Contents

Section 4 IEEE 488 Primer Page

4.7.6 Local Lockout (LLO) 4.8

4.7.7 Device Clear (DCL) 4.8

4.7.8 Selected Dev i ce Cl ear (SDC) 4.9

4.7.9 Serial Poll Disable (SPD) 4.9

4.7.10 Serial Poll Enable (SPE) 4.9

4.7.11 Group Execute Trigger (GET) 4.9

4.7.12 Take Control (TCT) 4.9

4.7.13 Secondary Command Group (SCG) 4.9

4.7.14 Parallel Poll Configure (PPC) 4.10

4.7.15 Parallel Poll Unconfigure (PPU) 4.10

4.8 More On Service Requests 4.10

4.8.1 Serial Poll 4.11

4.8.2 Parallel Poll 4.11

Section 5 Serv i ce Information Page

5.1 Factory Service 5.1

5.2 Theory of Operation 5.1

5.3 Digital488 Mother Board Component Layout 5.3

5.4 Digital488 I/O Board Component Layout 5.4

5.5 Digital488OEM Component Layout 5.5

5.6 Digital488 Parts List 5.6

5.7 Digital488OEM Parts List 5.8

Appendix A Digital488 Command Summary

Appendix B IEEE Command and Address Messages

Appendix C Digital488OEM Mechanical Dimensions

Section 1 Introduction

Introduction

1.1 General Description Digital488

The
Each unit has 40 TTL level digital I/O lines, which are divided into 5 eight-bit ports.
Each port is software programmable as input or output. The
board level interface with the same capabilities as the
this manual refer to both products unless otherwise stated. When the model number

Digital488

capability. A trigger output signal is asserted on the Group Execute Trigger (GET)
command. Edge-triggered inputs can generate a Service Request on the bus. Six data
formats are software programmable, including ASCII hexadecimal, ASCII character,
ASCII binary, binary, high speed binary and ASCII decimal. There are also
individual bit set and bit clear commands. Programmable terminators are provided
to facilitate interfacing to various controllers.

the
proper RAM and ROM operation.

is used in this manual,

Digital488

The

A status mode enables the controller to interrogate the programmed status of

Digital488

at any time. A self-test is initiated at power-on which checks for

is a digital input and output interface to the IEEE 488 bus.

Digital488OEM

Digital488

Digital488OEM

has several features which give it versatile interface

is also implied.

. All descriptions in

is a

When addressed to talk, the
a selected 8 bit port. When addressed to listen, the unit will input data and
programming information from the controller, and output the data to the appropriate
I/O port.

Digital 488

will output data from all forty bits or

1.1

Section 1 Introduction

1.2 Available Accessories

Additional accessories that can be ordered for the

CA-7-1
CA-7-2
CA-7-3
CA-7-4
CA-8-50

† 6 foot, 50 conductor ribbon cable with a card edge

1.5 foot IEEE 488 Cable
6 foot IEEE 488 Cable
6 foot shielded IEEE 488 Cable
6 foot reverse entry IEEE 488 Cable

Digital488

include:

connector on one end, the other end un-terminated.

CN-6-50
CN-20
CN-22

† 50 Pin solder tab edge connector.

Right Angle IEEE 488 adapter, male and female
IEEE 488 Multi-tap bus strip, four female connectors in
parallel

CN-23

IEEE 488 panel mount feed-through connector, male
and female

110-0920
Rack488-3
Rack488-4
TR-2
TR-2E

† 5-1/4" by 19" rack mount for one
† 5-1/4" by 19" rack mount for two

† 110 volt Wall mount power supply for the

† 220 volt Wall mount power supply for the

TR-5
TR-5E

†

For use with Digital488 Only

Additional Instruction Manual

Digital488
Digital488

110 volt Wall mount power supply for the
220 volt Wall mount power supply for the

Digital488
Digital488
Digital488OEM
Digital488OEM

s

1.2

Section 1 Introduction

1.3 Specifications

Digital488 Specifications
Digital I/O

Terminal Installation Category:

Standard: Not Applicable. CE: Category 1.

Transistor-Transistor Logic (TTL) Levels:

Outputs will drive 2 TTL loads.

Connector:

One 50-pin card edge (mating connector supplied).

IEEE 488

&$87,21

The IEEE 488 terminal must only be used to control a non-isolated IEEE 488 system.
The common mode voltage (cable shell to earth) must be zero.

Terminal Installation Category:

Standard: Not Applicable. CE: Category 1.

Implementation:

SH1, AH1, T6, TE0, L4, LE0, SR1, RL0, PP0, DC1, DT1, C0, E1.

Terminators:

Selectable CR, LF, LF-CR, and CR-LF with EOI.

Programmable:

IEEE Terminators, EOI, SRQ Mask, Port Data, Active Levels, Handshake Lines, Format and Configuration.

Connector:

Standard IEEE 488 connector with metric studs.

General

Configuration:

Five 8-bit ports, programmable as inputs or outputs. Also included are programmable handshake lines, data latching
capability, Clear and Trigger outputs, and a Service Request (SRQ) input.

1.3a

Section 1 Introduction

Terminal Installation Category:

Standard:

Dimensions:

188 mm deep x 140 mm wide x 68 mm high (7.39" x 5.5" x 2.68").

Weight:
Operating Environment:

Standard:
CE:

RH/°C to 40°C.

Controls:

Power switch (external), and IEEE parameter switches (internal).

Indicators:

LED indicators for IEEE TALK, LISTEN, SRQ, ERROR, and POWER.

Power:

An external power supply is provided with the Digital488: Input is 105-125 VAC,
or 210-250 VAC; 50/60 Hz, 10 VA maximum. The external power supply 9 VDC output is to be connected to the
Digital488 power input marked: 10 VDC MAX @ 500 mA.

Not Applicable.

1.55 kg. (3.6 lbs).

Indoor, 0° to 50°C; 0 to 70% RH to 35°C. Linearly derate 3% RH/°C from 35 to 50 °C.

Indoor use at altitudes below 2000 meters, 0° to 40°C; 80% maximum RH up to 31°C decreasing linearly 4%

CE:

Category 1 for all terminals.

:$51,1*

Do not use this interface outdoors! The interface is intended for indoor use only!
Outdoor conditions could result in equipment failure, bodily injury, or death!

&$87,21

Do not connect AC power line directly to the Digital488. Direct AC connection will
damage equipment.

1.3b

Section 1 Introduction

Digital488/OEM Specifications

:$51,1*

Do not use this interface outdoors! The interface is intended for indoor use only!
Outdoor conditions could result in equipment failure, bodily injury, or death!

&$87,21

Never disassemble the interface case while it is connected to the AC power line!
Internal voltage potentia ls exist which could cause bodily injury or death!

Digital I/O

Transistor-Transistor Logic (TTL) Levels:

Outputs will drive 2 TTL loads.

Connector:

One 50-pin IDC, organized as two rows of 25 pins.

IEEE 488

Implementation:

SH1, AH1, T6, TE0, L4, LE0, SR1, RL0, PP0, DC1, DT1, C0, E1.

Terminators:

Selectable CR, LF, LF-CR, and CR-LF with EOI.

Programmable:

IEEE Terminators, EOI, SRQ Mask, Port Data, Active Levels, Handshake Lines, Format and Configuration.

Connector:

Standard IEEE 488 connector with metric studs.

1.3c

Section 1 Introduction

General

Configuration:

Five 8-bit ports, programmable as inputs or outputs. Also included are programmable
handshake lines, data latching capability, Clear and Trigger outputs, and a Service Request (SRQ) input.

Dimensions:

205 mm deep x 115 mm wide x 28 mm high (8" x 4.5" x 1.1").

Weight:
Operating Environment:

Controls:

Indicators:

Power:

0.23 kg. (0.5 lbs).

Standard:

IEEE parameter switches.

LED indicators for IEEE TALK, LISTEN, SRQ, ERROR, and POWER.

User suupplied +5 volts ±0.25% at 1 amp. Mating power connector with 8 inch leads provided.

Indoor, 0° to 50°C; 0 to 70% RH to 35°C. Linearly derate 3% RH/°C from 35 to 50 °C.

:$51,1*

Do not use this interface outdoors! The interface is intended for indoor use only!
Outdoor conditions could result in equipment failure, bodily injury, or death!

&$87,21

Never disassemble the interface case while it is connected to the AC power line!
Internal voltage potentia ls exist which could cause bodily injury or death!

1.3d

Section 1 Introduction

1.4 Abbreviations

The following IEEE 488 abbreviations are used throughout this manual.

addr n IEEE bus address "n"

ATN Attention line

CA Controller Active

CR Car riage Return

data Data String

DCL Device Clear

GET Group Execute Trigger

GTL Go To Local

LA Listener Active

LAG Listen Address Group

LF Line Feed

LLO Local Lock Out

MLA My Listen Address

MTA My Talk Address

PPC Parallel Poll Configure

PPU Parallel Poll Unconfigure

SC System Controller

SDC Selected Device Clear

SPD Serial Poll Disable

SPE Serial Poll E nable

SRQ Service Request

TA Talker Active

TAD Talker Address

TCT Take Control

term Terminator

UNL Unlisten

UNT Untalk

* Unasserted

1.5

Section 2 Getting Started

Getting Started

2.1 Inspection Digital488

The
prior to shipment. When you receive the interface, carefully unpack all items from
the shipping carton and check for any obvious signs of physical damage which may
have occurred during shipment. Report any such damage found to the shipping agent
immediately. Remember to retain all shipping mater ials in the event that shipment
back to the factory becomes necessary.

Digital488

Every

was carefully inspected, both mechanically and electrically,

is shipped with the following....

•

Digital488

•

Digital488OEM

•

CN-8-50

•

110-0920

•

Power Supply

•

†

Supplied with Digital488 Only and not the Digital488OEM

† Digital I/O Port Mating Connector

† TR-2; 115V or

IEEE Digital I/O Converter or
Board Level IEEE Digital I/O Converter

Instruction Manual

TR-2E; 220V

2.2 Configuration

Digital488

The

has one internal 8 position switch wh ich determ ines the unit's
IEEE address and its default IEEE bus output terminator. The switch is only read
when the unit is powered on, and should only be set prior to applying power. The
following figure illustrates the f actory default setting for

SW1.

SW1 Factory Default Settings

12345678

0
1

IEEE Address = 18

Terminator = CR-LF

EOI Enabled

OPEN

Switch

Side
View

DOT

2.1

Section 2 Getting Started

To modify any of these defaults, follow this simple procedure. Disconnect the
power supply from the AC line and from the interface. Disconnect any IEEE or
digital I/O cables prior to disassembly.

WARNING
Never open the Digital488 case while it is
connected to the AC line. Failure to observe the
warning may result in equipment failure, personal
injury or death.

Remove the four screws located in each corner of the rear panel. Hold the case
firmly and pull the rear panel outward, noting the slot location of the main circuit
board. Modify those parameters which are appropriate for your installation and
reassemble the unit. Slide the main circuit board into the previously noted slot and
finish reassembly by tightening the four scr e ws into the rear panel.

2.2.1 IEEE 488 Address Selection

The IEEE 488 bus address is set by

SW1-1

address can be set from 0 through 30 and is read

address is selected by simple binary weighting with

significant bit and

SW1-5

the most significant bit. The factory default is

through

only

SW1-1

SW1-5.

The

at power on. The

being the least

address 18. If address 31 is selected, it defaults to address 30 because the

IEEE 488 standard has reserved address 31.

SW1 View for IEEE Bus Address Selection

12345678

0
1

OPEN

IEEE Address = 18

1 x 16
0 x 8
0 x 4
1 x 2
0 x 1

+

Switch

= 16

= 0
= 0
= 2
= 0

DOT

Side
View

2.2

Section 2 Getting Started

2.2.2 IEEE 488 Bus Output Terminator Selection

The terminating characters sent on output by the

determined by

SW1-6

through

SW1-8.

The terminator switches are read

Digital488

are

only at power on, but can be changed by the controller through the

Terminator

command. If power is cycled after receipt of the

Terminator

command, then the unit will once again default to the switch settings. The

factory default settings are Carriage Return - Line Feed with EOI asserted.

Digital488

The

controller. Only the

ignores all terminators received from the bus

Execute

command

(X)

is used to signal the

Digital488

that a command string has been completed.

SW1 View for Terminator Selection

12345678

0
1

OPEN

12345678

0
1

OPEN

Switch

Side
View

CR-LF LF-CR

12345678

0
1

OPEN

12345678

0
1

OPEN

CR Only LF Only

12345678

0

12345678

0

DOT

1

OPEN

1

EOI Enabled EOI Disabled

2.3

OPEN

Section 2 Getting Started

2.3 Digital Input/Output Ports

Digital488

The

has 40 data lines which can be programmed in groups of 8 as
either input or output. At power on, all 40 bits are in the input mode. Each 8 bit group
is one port, beginning with

Port 1

as the least significant 8 bits, and

Port 5

as the most

significant 8 bits.

2.3.1 Logic Levels

The data and handshake output lines will drive two TTL loads. In
addition, ports 1 and 2 outputs are 5 Volt CMOS compatible. All input lines are
less than 1.5 TTL loads. All inputs are protected against damage due to high
static voltages. Normal precautions should be taken to limit the input voltages
to -0.3 to +7.0 volts. All I/O lines are referenced to

COMMON

(Pin 50).

2.3.2 Digital I/O Port Pin Outs

The following diagram illustrates the digital I/O edge connector as view

.

Digital488

and the top PC Board edge view of the

from the rear of the

Digital488OEM

Digital I/O

Bits 1 thru 40

Digital488 Rear Panel I/O Connector Pin Out

External Data Ready (I)

210 20 30 40 50

(I)

= Input

(O)

= Output

Inhibit (O)

Data Strobe (O)

Clear (O)

Trigger (O)

Service (I)

2.4

Not Used
Common (GND)

4939199129

+5 Volts
[ 50 mA Max!]
Not Used

Section 2 Getting Started

Digital488OEM I/O Connector Pin Out

External Data Ready (I)

210 20 30 40 50

Digital I/O

Bits 1 thru 40

PC Board Edge

(I)

= Input

(O)

= Output

Pin Description

1 thru 8

DATA PORT1

Pin 1 is bit 1 (LSB), Pin 8 is bit 8 (MSB).
Least Significant Port

9 thru 16

DATA PORT2

Pin 9 is bit 1 (LSB), Pin 16 is bit 8 (MSB).

17 thru 24

DATA PORT3

Pin 17 is bit 1 (LSB), Pin 24 is bit 8 (MSB).

25 thru 32

DATA PORT4

Pin 25 is bit 1 (LSB), Pin 32 is bit 8 (MSB).

Inhibit (O)

Data Strobe (O)

Clear (O)

Trigger (O)

Service (I)

(Input or Output).

(Input or Output).

(Input or Output).

(Input or Output).

Not Used
Common (GND)

4939199129

+5 Volts
[ 50 mA Max!]
Not Used

33 thru 40

41

42

43

44

DATA PORT5

(Input or Output).
Pin 33 is bit 1 (LSB), Pin 40 is bit 8 (MSB).
Most Significant Port

CLEAR
DATA STROBE
TRIGGER
INHIBIT

(Output).

(Output).

(Output).

(Output).

2.5

Section 2 Getting Started

45

46

SERVICE INPUT

(Input).

EXTERNAL DATA READY [EDR]

47,48 Not used.

49

50

+5 Volts
I/O COMMON (Gnd).

Do not exceed 50 mA load

(

2.3.3 Control Lines

Five control lines enable handshaking of digital I/O data transfer to the

Digital488

. They are automatically activated with the corresponding I/O
activity and can also be independently activated with the
command.

2.3.3.1 Clear

The

(Pin 41)

Clear

output is pulse for approximately 50
microseconds after a Device Clear (DCL), Selected Device Clear
(SDC), or Interface Clear (IFC) command has been sent on the bus.

Clear

The

line is normally active high. The
will program it active low. The
pulse the

Clear

line, independent of any I/O operations.

Handshake

Invert

command

(Input).

).

Handshake

command (I8)

(H0)

can

(Hn)

Timing Diagram for Clear Output

DCL, SDC or IFC

Clear

65 µS typ 50 µS typ

2.6

Section 2 Getting Started

2.3.3.2 Data Strobe

Data Strobe

The

microseconds after new data is output on the I/O port. The

Strobe

low by the
can pulse the

line is normally active high but may be programmed active

Invert

Data Strobe

(Pin 42)

output is pulse for approximately 50

command (I4). The

line, independent of an I/O operations.

Handshake

command

Data

(H1)

Timing Diagram for Strobe Output

DATA

15 µS min

DATA VALID

50 µS typ†

STROBE

† 15 µS typ in F5 Format

2.3.3.3 External Data Ready [EDR]

External Data Ready [EDR

The

(Pin 46)

] line is an edge sensitive

input which is used to latch input data. It is used in conjunction with

Data Ready

the

command (R1). The

EDR

signal must be at least 1
microsecond wide and must have a rise and fall time of less than one
microsecond. The
be programmed with the

EDR

line is normally rising-edge sensitive but can

Invert

command (

I32

) to be falling-edge

sensitive. Refer to the following diagram for timing r e lationships.

When using the

read when the

Digital488

will only output data when the

EDR

is not functional in the high speed binary (F5) format.

EDR

Digital488

line with the R1 command, data is not

is addressed to talk as with R0. The

EDR

line transitions.

2.7

Section 2 Getting Started

2.3.3.4 Inhibit

The

(Pin 44)

Inhibit

output is asserted while data on the selected I/O
port is being read into the I/O port buffer. This line is normally active
high but may be programmed active low by the

Inhibit

The
operations with the

line can be programmed independent of any I/O

Inhibit

command (Qn). Refer to the following

Invert

command (I1).

diagram for timing relationships.

Inhibit

The

line is asserted once for each data read operation
for all format [Fn] modes except high speed binary [F5]. In this mode,
it is asserted for the first data read after the
talk. On the last data byte transfer, the data is read again with
asserted in anticipation of another data transfer. If

Digital488

Inhibit

is addressed to

Inhibit

is used to
sequence external hardware, you should be aware that this line will
pulse N+1 times; where N is the number of total (5 byte) data
transfers.

Timing Diagram for EDR Input and Inhibit Output

50 µS typ

INHIBIT

DATA

DATA VALID

1 µS min

EDR

10 µS min

50 µS max

50 µS typ

2.8

Section 2 Getting Started

2.3.3.5 Trigger

The

microseconds after a

(Pin 43)

Trigger

output is pulse for approximately 50

GET

(Group Execute Trigger) command is
received from the bus controller. The trigger pulse is normally active
high, but can be made active low with the

Handshake

command (H2) can independently pulse the

Invert

command (I2). The

Trigger

line,

independent of any bus activity.

Timing Diagram for Trigger Output

GET

Trigger

75 µS typ 50 µS typ

2.3.3.6 Service

The
generating a bus
command (M1) and defaults to rising-edge sensitive. The
command (

(Pin 45)

Service

I64

) can be used to program it to be falling-edge sensitive.

input is an edge sensitive input capable of

Service Request (SRQ).

It is enabled with the

SRQ

Invert

2.4 IEEE 488 Bus Implementation

Digital488

The

implements many of the capabilities defined by the IEEE 488

1978 specification. These are discussed in the following sections. Those bus uniline
and multiline commands that the

Remote Enable
Go to Local
Local Lockout
Take Control

(REN)

(GTL)

(LLO)

(TCT)

Digital488

does not support or respond to include:

Parallel Poll
Parallel Poll Configure
Parallel Poll Unconfigure
Parallel Poll Disable

(PP)

(PPC)

(PPU)

(PPD)

2.9

Section 2 Getting Started

2.4.1 My Talk Address

When the

the data from all ports, un-asserts
the format as defined by the Fn, Pn and
terminators are appended to the output with the exception of the F4 and
formats. F4 does not append terminators. The output format of F5 will be
described separately. After output in the F0 through F4 formats, the

Digital488

In the R1 mode, it will wait for the selected

reading the data and formatting it for output. If the
prior to being addressed to talk, the data read at the time of
buffered for output when next addressed to talk. If
before the previous
generate an
output in the F0 through F4 formats, the
talk to perform subsequent buffered output of

In either Rn mode, the

without affecting the data ports or
output, the presently programmed Rn mode returns.

EDR

(F5). When addressed to talk in this format it asserts
from all ports, un-asserts
EOI asserted on the fifth byte. When the last data byte is trans ferred, the d ata
is read again in anticipation of another data transfer. If
sequence external hardware, this line will pulse N+1 times; where N is the
number of total (5 byte) data transfers. In this format t he
have to be re-addressed to talk to read the ports multiple times.

Digital488

must be re-addressed to talk to perform subsequent reads.

EDR Overrun

cannot be used to capture data in the high speed binary format

(MTA)

is addressed to talk (R0) it asserts

Inhibit

buffered data has been output, the

EDR

error and ignore the

Digital488

and outputs the binary data to the bus with

Inhibit

and outputs the data to the bus in

commands. The output bus

Gn

Digital488

EDR

can send requested status (Un)

. After the requested status is

Inhibit

, reads

Inhibit

transition before

EDR

line has transitioned

EDR

will be

EDR

transitions again

EDR

Digital488

read request. After

EDR

must be re-addressed to

captured data.

, reads the data

Inhibit

is used to

Inhibit

Digital488

does not

F5

will

With all Fn formats, the data is output in a PORT5, PORT4, PORT3,
PORT2, PORT1 sequence.

2.10

Section 2 Getting Started

2.4.2 My Listen Address

When the

format, it accepts characters from the active talker and interprets these
characters as commands and command parameters. These commands are
explained in Section 3.

In the high speed binary format (F5), the command interpreter is

disabled. The
Digital I/O ports. Each time it receives five bytes or detects EOI it pulses the

Data Strobe

PORT5, PORT4, PORT3, PORT2, PORT1 sequence.

If only two bytes are received, with EOI asserted on the second byte,

Digital488

the
the second and pulse the
characters as data, the

2.4.3 Device Clear

In the F0 thru

power on defaults and pulses the
microseconds.

In the high speed binary format (F5), it enables the command

interpreter and changes the format to F0. All other parameters remain
unchanged. In addition, the
when the interface is in F5. This is the only programmable method to exit the

F5

format.

Digital488

Digital488

for approximately 15 microseconds. Data is expected in a

will update PORT5 with the first byte received, PORT4 with

(MLA)

is addressed to listen in the F0 through

treats all bytes received as data to be output to the

Data Strobe

Status (Un

(DCL and SDC)

F4

formats, Device Clear resets the

Clear

. Since the interface treats all received

) command will not be recognized.

Digital488

Clear

output line for approximately 50

output line is not pulsed by DCL or SDC

F4

to

2.4.4 Group Execute Trigger

When the

line for approximately 50 microseconds.

Digital488

(GET)

recognizes a GET, it pulses the

2.11

Trigger

output

Section 2 Getting Started

2.4.5 Interface Clear

IFC places the

Clear

the

2.4.6 Serial Poll Enable

serial poll with its serial poll status byte if addressed to talk. When the serial
poll byte is accepted by the controller, any pending

Digital488

serial poll disabled by the controller.

2.4.7 Serial Poll Disable

controller.

2.4.8 Unlisten

2.4.9 Untalk

output line for approximately 50 microseconds.

When Serial Poll Enabled, the

will continue to try to output its serial poll response until it is

Disables the

UNL places the

(UNT)

(UNL)

(IFC)

Digital488

(SPE)

(SPD)

Digital488

Digital488

in the Talker/Listener Idle State and pulses

Digital488

from responding to serial polls by the

in the Listener Idle State.

sets itself to respond to a

SRQ

s are cleared. The

UNT places the

Digital488

in the Talker Idle State.

2.12

Section 2 Getting Started

2.5 Installation

To begin operating the

jack on the interface.

Never install the power supply into the interface
while it is connected to AC line power. Failure to
observe this caution may result in damage to the
Digital488.

The power supply provided with the interface is
intended for INDOOR USE ONLY. Failure to
observe this warning could result in equipment
failure, personal injury or death.

After installing the power supply connector into the interface, turn on the

Digital488

light for approximately one second while the
and RAM self check. At the end of this self check all indicators should turn off except

POWER

LEDs remain on, then a ROM error has occurred. If all LEDs continue to flash (except
the power LED), then a RAM error has occurred. Try cycling the power to the

Digital488

by depressing the rear panel power switch. All the front panel LEDs should

.

If you obtain the above response then your

to determine that the error is repeatable.

Digital488,

plug the external power supply into the rear

CAUTION

WARNING

Digital488

Digital488

performs an internal ROM

is alive and well. If all

If the LEDs do not flash and the
may not be any power supplied to the interface. In this event, check to make sure the
AC power is supplied to the power supply, and that the supply is properly installed into
the unit. If the problem is unresolved, refer to the
manual.

POWER

indicator does not remain lit, there

Service Information

2.13

section of this

Section 3 Command Descriptions

Command Descriptions

Control of the Digital 488 is implemented with 17 bus commands, described here

in detail. Examples are given for many of the commands using a Hewlett-Packard 85
computer in the immediate mode. It is implied that each command is terminated by the
'END LINE' key on the HP-85 in order to execute the command. The Digital488 bus
address should be set to 18 for all examples.

Attention!

It is necessary that the EXECUTE command (X) follow
all command strings sent to the Digital488. No commands
are executed until an X is received by the Digital488.

3.1

Section 3 Command Descriptions

Bit Set An

Bit Set

The
argument 'n'. Setting a bit may represent either a +5 volt or 0 volt output, depending on
whether an
then
string, an

Configure

command is sent.

Example:

Invert

Bit Set

Execute

The bit which is being set must have been configured as an output bit by the

command to be valid. The

An

Bit n (1 thru 40) is set to logic one

command programs a logic one output to a bit described by the

command (

outputs +5 volts. If multiple bits are to be set within the same command

command (X) must be included after every

I16)

has been sent. If data is active high (default condition),

Strobe

Bit Set

output line is not pulsed when the

command.

Bit Set

CLEAR 718
OUTPUT 718;"C5X"
OUTPUT 718;"A22X"
OUTPUT 718;"A23XA24X"

reset the
configure all ports as output
set bit 22 to a logic one
set bits 23 and 24 to a logic one

Digital488

3.2

Section 3 Command Descriptions

Bit Clear Bn

Bit Clear

The
argument 'n'. Clearing a bit may represent either a 0 volt or +5 volt output, depending
on whether an
condition), then
used in the same command string, an
command.

The bit which is being cleared must have been defined as an output by the

Configure

the

Example:

command in order to be valid. The

Bit Clear

Bn

Bit n (1 thru 40) is cleared to a logic 0

command will clear to a logic zero an output bit described by the

Invert

command (

Bit Clear

command is sent.

I16

) has been sent. If data is active high (default

outputs 0 volts. When multip le

Execute

command (X) must follow each

Strobe

output line is not pulsed when

Bit Clear

commands are

CLEAR 718
OUTPUT 718;"C5X"
OUTPUT 718;"A7XA8XA9X"
OUTPUT 718;"B7X"
OUTPUT 718;"B8XB9X"

reset the
configure all ports as output
set bits 7, 8, and 9 to +5 volts
clear bit 7 to zero volts
clear bits 8 and 9 to zero volts

Digital488

3.3

Section 3 Command Descriptions

Bus Input/Output Gn

Bus Output

The
or both will be transmitted on the bus when the
amount of data sent is dependent on the Pn command.

The G0 default mode causes all input and output port data to be sent to the
controller when addressed to talk. The G1 mode causes only data from the ports
programmed as inputs to be returned when addressed to talk. The G2 mode causes only
data from ports programmed as outputs to be returned when addressed to talk.

command determines whether input port data, output port data

Digital488

is addressed to talk. The

If all ports are programmed as outputs with G1 selected and the
addressed to talk, nothing will be transmitted and the bus will hang. The conver se will
also cause the bus to hang with all ports programmed as inputs and G2 selected.

G0

G1

G2

Example:

CLEAR 718
OUTPUT 718;"P0C1X"
OUTPUT 718;"G1X"
ENTER 718; A$
DISP A$

OUTPUT 718;"G2X"
ENTER 718; A$
DISP A$

Input and output
Only input port data is sent on talk
Only output port data is sent on talk

port data is send on talk

reset the
port1 as output, ports 2-5 as input
select only input ports
read data from the input ports
display shows
dependent on what is connected.

select output ports
read data from the output ports
display shows 00 (outputs default to 0)

Digital488

FFFFFFFF

Digital488

(data is

is

3.4

Section 3 Command Descriptions

Configure Cn

Ports 1 thru 5 are configured as inputs or outputs with the
Each port is eight bits wide. At power-on, all ports are initialized as inputs. The

Configure

programmed as outputs will be set to a logic zero after receiving the
command. The actual output level is dependent on the

Example:

CLEAR 718
OUTPUT 718;"C1X"

command is usually the first command to be sent after power on. All ports

Invert

Cn

Mode n (0 thru 5) defines which ports are input and output

Port 5
C0

in in in in in

C1

in in in in out

C2

in in in out out

C3

in in out out out

C4
C5

in = programmed as an input port
out = programmed as an output port

4 3 2 1

in out out out out
out out out out out

reset the
select port 1 as output, ports 2 thru 5
as inputs

Digital488

Configure

command (

command.

Configure

I16).

3.5

Section 3 Command Descriptions

Data Dn....Z

Data

The
of bits which can be sent with the
programmed as outputs. For formats F0 through F3, if the amount of data sent is less
than the the number of bits programmed as outputs, the least-significant bits will con tain
the data sent and the most-significant bits will be cleared to lo gic zero. If a sing le port is
selected with the

Data Strobe

on the selected ports.

For formats F0 through F3, data sent by the controller is contained within a prefix
(D) and a suffix (Z). In format F4, the five bytes immediately following the prefix (D) is
interpreted as data and the suffix (Z) is not used. For the high speed binary F5 format,
all bytes received are treated as data and the prefix and suffix are not used. Refer to the

Fn

command for additional details.

command outputs up to 40 bits of data to the output ports. The number

Data

command is limited by the number of bits

Port

command, only eight bits may sent with the

output is pulse for approximately 50 microseconds after new data is output

Data

command. The

Dn...Z

(note: in the F4 mode, the Z terminator is not allowed)

Example:

CLEAR 718
OUTPUT 718;"C5P1X"
OUTPUT 718;"D55ZX"
ENTER 718; A$
DISP A$

OUTPUT 718;"P0X"
OUTPUT 718;"D1234567890ZX"
ENTER 718;A$
DISP A$

n...

represents the data to be outputted, terminated by Z.

reset the
all ports as output, select port 1
send 55 to port 1
read data from port 1
display shows

select all ports
send data to all 40 bits
read data from the Digital488
display shows

Digital488

55

1234567890

3.6

Section 3 Command Descriptions

OUTPUT 718;"D123ZX"
ENTER 718; A$
DISP A$

OUTPUT 718;"P5D21ZX"
OUTPUT 718;"P0X"
ENTER 718; A$
DISP A$

send 12 bits of data to the least significant bits
read data from the Digital488
display shows

set port 5 only
select all ports
read data from the Digital488
display shows

0000000123

2100000123

3.7

Section 3 Command Descriptions

Data Ready Rn

Data Ready

The
conjunction with the
can both latch the input data and signal the controller that new data is av ailable.

command enables digital input data to be latched. When used in

Service Request (M2

) command, the

External Data Ready

line

In the default mode (R0) data is read when the
the R1 mode, it will wait for the selected
reading the data and formatting it for output. If the

EDR

is asserted, the bus will hang up until the
the data will remain latched until the interface is addressed to talk and the d ata is read by
the controller. If
output, the
request.

After output in the F0 through F4 formats, the
talk to perform subsequent buffered output of
to capture data in the

The
fall time of less than 1.0 microsecond. The
can be changed to falling-edge sensitive with the

R0

R1

Data is latched on an

Example:

CLEAR 718
OUTPUT 718;"R1X"

EDR

transitions again before the previous

Digital488

EDR

will generate an

F5

high speed binary format

signal must be at least 1 microsecond wide and should have a rise and

Data is not latched, and is read whenever the
is addressed to talk

External Data Ready (EDR

EDR Overrun

EDR

EDR

EDR

Digital488

Digital488

EDR

pulse occurs. Once

error and ignore the

Digital488

captured data.

line defaults to rising-edge sensitiv e, but

Invert

command (

transition

reset the
data is only read after a rising-edge
signal is applied to the

is addressed to talk. In

) transition before

is addressed to talk before

EDR

is asserted

EDR

buffered data has been

EDR

must be re-addressed to

EDR

cannot be used

I32

).

Digital488

Digital488

EDR

line

read

3.8

Section 3 Command Descriptions

End or Identify (EOI) Kn

EOI

The
is used by a talker to indicate the end of a multiple by te transfer sequ ence. At power ­on, the setting of Switch S1 determines the default
change the

EOI

the

K1

In the
[F4 and F5] )

line is one of five interface management lines on the IEEE 488 Bus. It

EOI

mode. The controller can

EOI

mode by programming the

line is asserted by the

mode the

.

EOI

function is disabled (except when using the binary modes

Digital488

Digital488

on the last byte of every bus output string.

from the bus. In the

K0

mode,

K0 EOI

K1 EOI

Example:

OUTPUT 718;"K1X"

enabled, assert

disabled, do not assert

EOI

on last byte transferred

EOI

on last byte transferred

disables EOI on last byte

3.9

Section 3 Command Descriptions

Execute X

Commands sent to the
instructed to execute these commands. This is done by sending an X, usually as the last
character of a command string. Commands sent without an X are stored in the internal
buffer until an X is received. Any number of
the same command string. Certain commands, such as
command in a string if more than one of that command is within the same string.

Example:

CLEAR 718
OUTPUT 718;"F2"

OUTPUT 718;"X"

OUTPUT 718;"A1XA2X"

Digital488

will result in no action until the unit is

Execute

reset the
send "F2" to the
input buffer
instruct the
command input buffer
two Bit Set (A) commands are within the
same string, requiring an X after each
command.

commands may be inserted into

Bit Set

require an X after each

Digital488

Digital488

Digital488

command

to execute its

3.10

Section 3 Command Descriptions

Format Fn

Format

The
be described. Six data formats are available.

command determines the method by which input and output data will

F0

ASCII Hexadecimal (4 bits per character)

F1

ASCII Character (4 bits per character )

F2

ASCII Binary (1 bit per character)

F3

ASCII Decimal (8 bits per number)

F4
F5

Binary (each byte represents 8 bits)
High Speed Binary (each byte represents 8 bits)

F0 Format- ASCII Hexadecimal

In the default
character having a value from 0 thru 9 or A thru F. Each ASCII character describes 4
bits of data.

Data received for output to the digital ports must be contained within a prefix (D)
and a suffix (Z). If the amount of data sent is less than the number of bits programmed as
outputs, the least-significant bits will contain th e data sent and the most-significant bits
will be cleared to logic zero. If the data sent is greater than the number of bits
programmed for output or selected by the Pn command, the
conflict error and ignore the entire command string. The
approximately 50 microseconds after new data is output on the selected port(s).

F0

format, the data is described in ASCII hexadecimal, with each

F0 Character Decimal Equiv

00 8 8
11 9 9
22 A 10
33 B 11
44 C 12
55 D 13
66 E 14
77 F 15

F0 Character Decimal Equiv

Digital488

Data Strobe

will generate a

output is pulse for

3.11

Section 3 Command Descriptions

When the
from all ports, u nasserts

Gn

appended to the output. After output the
perform subsequent reads.

Example:

DIM A$[50]
CLEAR 718
OUTPUT 718;"C2G2X"
OUTPUT 718;"D4E6BZX"
ENTER 718; A$
DISP A$

four least significant bits of each ASCII character representing four bits of data.

Pn

and

In the F1 format, the data is coded and transmitted in ASCII Characters with the

F1 Character Decimal Equiv

Digital488

commands. Leading zeros are not suppressed and the bus terminators are

00 88
11 99
22 :10
33 ;11
44 <12
55 =13
66 >14
77 ?15

is addressed to talk (R0) it asserts

Inhibit

and outputs the number of characters determined by the

Digital488

EDR (R1

) may also be used to capture data in this format.

dimension the length of A$
reset the
configure ports 1 & 2 as output
output hexadecimal
read data from the
display shows

F1 Format - ASCII Character

F1 Character Decimal Equiv

must be re-addressed to talk to

Digital488

4E6B

Digital488

4E6B

to ports 1 & 2

Inhibit

, reads the data

Data received for output to the digital ports must be contained within a prefix (D)
and a suffix (Z). If the amount of data sent is less than the number of bits programmed as
outputs, the least-significant bits will con tain the data sent and the most-significant bits
will be cleared to logic zero. If the data sent is greater than the numb er of bits programmed
for output or selected by the Pn command, the
and ignore the entire command string.

Digital488

3.12

will generate a conflict error

Section 3 Command Descriptions

Data Strobe

The
data is output on the selected port(s).

output is pulse for approximately 50 microseconds after new

When the
from all ports, u nasserts

Gn

appended to the output. After output the
perform subsequent reads.

Example:

OUTPUT 718;"F1X"
ENTER 718; A$
DISP A$
OUTPUT 718;"D1??2ZX"
ENTER 718; A$
DISP A$

formatted in two 4-bit multiples separated by semicolons.

Pn

and

In the F2 format, the each data bit is described with an ASCII 0 or 1. Each byte is

F2 String Decimal Equiv
0000;0000 0 0000;1001 9
0000;0001 1 0000;1010 10
0000;0010 2 0000;1011 11
0000;0011 3 0000;1100 12
0000;0100 4 0000;1101 13
0000;0101 5 0000;1110 14
0000;0110 6 0000;1111 15
0000;0111 7 1000;0001 129
0000;1000 8 1111;1111 255

Digital488

commands. Leading zeros are not suppressed and the bus terminators are

is addressed to talk (R0) it asserts

Inhibit

and outputs the number of characters determined by the

Digital488

EDR (R1

) may also be used to capture data in this format.

select ASCII Character format
read data from the
display shows

1??2

send
read data from the
display shows

F2 Format - ASCII Binary

F2 String Decimal Equiv

to the

Inhibit

, reads the data

must be re-addressed to talk to

Digital488

4>6;

Digital488

Digital488

1??2

3.13

Section 3 Command Descriptions

Data received for output to the digital ports must be contained within a prefix
(D) and a suffix (Z) and each 4-bit quantity must be separated by semicolons. Leadin g
zeros are not required. If the amount of data sent is less than the number of bits
programmed as outputs, the least-significant bits will contain the data sent and the
most-significant bits will be cleared to logic zero. If the data sent is g reater than the
number of bits programmed for output or selected by the Pn command, the
will generate a conflict error and ignore the entire command string. The
output is pulse for approximately 50 microseconds after new data is output on the
selected port(s).

Digital488

Data Strobe

When the
from all ports, un asserts
the Gn and
are appended to the output. After output the
perform subsequent reads.

Example:

OUTPUT 718;"F2X"
ENTER 718;A$
DISP A$

OUTPUT 718;"D1111;0;1010;0101ZX"
ENTER 718; A$
DISP A$

In the

in ASCII. Each decimal number (0 to 255) to be output must be separated by semicolons.

Digital488

Pn

commands. Leading zeros are not suppressed and the bus terminators

F3

format, the data is described in decimal 8 bit multiples an d transmitted

is addressed to talk (R0) it asserts

Inhibit

and outputs the number of characters determined by

Digital488

EDR (R1

) may also be used to capture data in this format.

select ASCII/binary mode
read data from the
display shows

read data from the
display shows

F3 Format - ASCII Decimal

must be re-addressed to talk to

0001;1111;1111;0001

1111;0000;1010;0101

Inhibit

Digital488

Digital488

, reads the data

3.14

Section 3 Command Descriptions

F3 Number Decimal Equiv

000 0 008 8
001 1 009 9
002 2 010 10
003 3 020 20
004 4 100 100
005 5 200 200
006 6 210 210
007 7 255 255

Data received for output to the digital ports must be contained within a prefix (D)
and a suffix (Z). If the amount of data sent is less than the number of bits programmed as
outputs, the least-significant bits will contain th e data sent and the most-significant bits
will be cleared to logic zero. If the data sent is greater than the number of bits
programmed for output or selected by the Pn command, the
conflict error and ignore the entire command string. The
approximately 50 microseconds after new data is output on the selected port(s).

When the
from all ports, u nasserts

Gn

appended to the output. After output the
perform subsequent reads.

Example:

and

Pn

Digital488

Inhibit

commands. Leading zeros are not suppressed and the bus terminators are

EDR (R1

F3 Number Decimal Equiv

Digital488

Data Strobe

is addressed to talk (R0) it asserts

and outputs the number of characters determined by the

Digital488

) may also be used to capture data in this format.

must be re-addressed to talk to

will generate a

output is pulse for

Inhibit

, reads the data

OUTPUT 718;"F3X"
ENTER 718; A$
DISP A$
OUTPUT 718;D100;200ZX
ENTER 718; A$
DISP A$

select decimal mode
read data from the

100

240;165

200

&

100;200

3.15

display shows
output
read data from the
display shows

Digital488

Digital488

to the

Digital488

Section 3 Command Descriptions

F4 Format - Binary

In the F4 binary format, no error checking is performed and caution
exercised when using this mode to avoid locking the IEEE bus.

When addressed to listen, the
bytes of data beginning with PORT5 without the "Z" suffix. If any digital I/O port is
configured as an input, the data to that input port will be ignored.

When the
from all ports, u nasserts
asserted on the last bye. Bus terminators, with the exception of EOI, are
the output. After output the
subsequent reads.

In the F5 high speed binary format, the command interpreter is disabled. When
addressed to listen, the
Digital I/O ports. Each time it receives five bytes or detects EOI asserted, it pulses the

Data Strobe

PORT3, PORT2, PORT1 sequence. If only two bytes are received, with EOI asserted on
the second byte, the
with the second and pulse the
characters as data, the Un command will not be recognized.

Digital488

EDR (R1

for approximately 15 microseconds. Data is expected in a PORT5, PORT4,

Digital488

is addressed to talk (R0) it asserts

Inhibit

) may also be used to capture data in this format.

Digital488

Digital488

and outputs 5 bytes beginning with PORT5 with EOI

Digital488

F5 Format - High Speed Binary

treats all bytes received as data to be output to the

will update PORT5 with the first byte received, PORT4

Data Strobe

expects the "D" prefix followed by five

Inhibit

not

must be re-addressed to talk to perform

. Since the interface treats all received

must

be

, reads the data

appended to

To place the
the last command sent to the interface
this command, such as carriage return or line feed, will be considered data and the output
ports will reflect those character values.

When addressed to talk in th is format it asserts
ports, unasserts
fifth byte. When the last data byte is transferred, the data is read again in anticipation of
another data transfer. If
N+1 times; where N is the number of total (5 byte) data transfers. In this format the

Digital488

cannot be used to capture data in the

does

Digital488

Inhibit

and outputs the binary data to the bus with EOI asserted on the

Inhibit

not

have to be re-addressed to talk to read the ports multiple times.

in the F5 format, the 3 character string "

without

is used to sequence external hardware, this line will p ulse

F5

high speed binary format.

terminators. Any characters appended to

Inhibit

3.16

, reads the data from all

F5X

" should be

EDR

Section 3 Command Descriptions

The only programmable method to exit the F5 high speed binary format is device

DCL

clear (
interpreter and changes the format to F0. All other parameters remain unchanged. In
addition, the

) or Selected Device Clear (

Clear

output line is not pulsed by DCL or SDC when the interf ace is in F5.

SDC

). When received, it enables the command

3.17

Section 3 Command Descriptions

Handshake Hn

Handshake

The
independent of any other I/O operations. When the
respective handshake line is pulsed for approximately 50 microseconds. It returns to its steady­state condition after pulsing. The
any of the handshake lines.

control command enables software control of the handshake lines,

Digital488

Invert

command may be used to change the active state of

receives an Hn command, the

H0

H1

H2

Example:

OUTPUT 718;"H1X"

The
The
The

Clear

line is pulsed

Strobe
Trigger

line is pulsed

line is pulsed

the Strobe line is pulsed

3.18

Section 3 Command Descriptions

Inhibit Qn

Inhibit

The
independent of any other I/O activities. The 'set' and 'clear' levels of the
determined by the

Q0

Q1

Example:

CLEAR 718
OUTPUT 718;"Q1X"

control command allows software control of the

Invert

command.

Clear the
Set the

Inhibit

Inhibit

line (return to unasserted state)

line (place in the asserted state)

reset the
set the Inhibit line

Digital488

Inhibit

Inhibit

line,

line are

3.19

Section 3 Command Descriptions

Invert In

Invert

The
lines. At power up all handshake and control lines are active high (logic one = + 5
volts). The
handshake lines, and of the data lines. If multiple
within the same string, then an

Invert

each
desired, and send one command with the sum of the desired commands. The
commands are ORed together as received. To delete any one command, it is necessary
to program the default mode I0, then reprogram the desired commands.

command is used to change the polarity of the handshake and data

Invert

command can selectively change the polarity of each of the

Invert

commands are contained

Execute

command. An alternative is to add the values of each

command (X) should be included between

Invert

command

Invert

I0

I1 Inhibit

I2 Trigger

I4 Data Strobe

I8 Clear

I16 Data

I32 EDR

I64 Service

Example:

CLEAR 718
OUTPUT 718;"I32XI64X"

Note:

OUTPUT 718;"I96X"

All control lines are active high, all data lines are high true

output is active low

is low true

input is falling-edge sensitive

output is active low

output is active low

output is active low

input is falling-edge sensitive

reset the
select EDR and Service input as
falling-edge sensitive

performs the same function as above

Digital488

3.20

Section 3 Command Descriptions

Port Pn

Port

The
the default mode (P0), all ports are selected. The
specific eight bit port.

command determines which port is selected for data input/output. In

P1

thru P5 commands select a

It is recommend that the
determine which ports will be output when the
Data in modes

P0

P1

P2

P3

P4

P5

Example:

CLEAR 718
OUTPUT 718;"P4X"

P1

throuth

All five ports are selected
Port 1 is selected
Port 2 is selected
Port 3 is selected
Port 4 is selected
Port 5 is selected

Bus Output

P5

will be input or output in groups of eight bits.

command be used with the

reset the
select port 4

Digital488

Digital488

PO

mode to

is addressed to talk.

3.21

Section 3 Command Descriptions

Service Request Mask (SRQ) Mn

Service Request (SRQ)

The
controller to one of several condition s described below. Multiple
be enabled simultaneously by issuing them sepatately or by combining them in one
command. If multiple

SRQ

each
programmed
controller sends a Device Clear (DCL), Selected Device Clear (SDC), or Interface Clear
(IFC) command.

generating a

transition. Refer to the
of the

Refer to the

EDR

command should be followed by an

SRQ

M0

M1

M2

M4

M8

M16

MO

default mode disables the

Service Request

M1

will generate a

Service

input line.

input line.

M2

will generate a

Invert

SRQ

commands are contained within the same command string,

modes will remain enabled until the M0 command is sent, or the

SRQ is disabled
SRQ on
SRQ on
SRQ on bus error
SRQ on Self-Test error
SRQ on Ready

command

Service
EDR

.

Service Request

Invert

command

Service Request

(I32)

mode is used by the

Execute

input transition

input transition

SRQ

function, preventing the

when the

(I64)

description for programming the polarity

when the

description for programming the polarity of the

Digital488

SRQ

conditions can

command

Digital488

Service

EDR

Input line makes a

input makes a transition.

to alert the

(X).

The

from

M4

will generate a
common bus error is sending an invalid command to the
attempting to select an 'F6' format when no 'F6' format exists will ge nerate a

Request

when the M4 mode is selected.

Service Request

when a bus error occurs. The most

Digital488

3.22

. For example,

Service

Section 3 Command Descriptions

M8

will generate a
Refer to the

execution of a set of commands from the bus controller. This is used by the
controller to assure the completion of a set of commands before sending a
subsequent set of commands.

Example:

CLEAR 718
OUTPUT 718;"M4X"
OUTPUT 718;"F7X"

CLEAR 718
OUTPUT 718;"M1XM4X"

OUTPUT 718;"M5X"

Test

M16

will generate a

command

Service Request

(T0)

description for details on self-tests.

Service Request

reset the
select SRQ on Bus error
send an invalid bus command.

Note: ERROR and SRQ LEDs should illuminate

reset the
select SRQ on Bus error and SRQ on Service input.

This has the same effect as the command above
where

when the

when the

Digital488

Digital488

M1X

plus

Digital488

M4X

equals

Digital488

M5X

self-test fails.

has completed the

.

3.23

Section 3 Command Descriptions

Serial Poll Status Byte

Serial Poll Output

The
from the controller. Refer to the
byte is affected. Below is a description of the significance of each bit in the
byte.

byte is sent upon receiving the serial poll command

SRQ

description for details on how the

Serial Poll

Serial Poll

Bit Location Significance
DIO1(LSB) 1 Service Input transition
DIO2 2 EDR input transition
DIO3 4 Bus error
DIO4 8 Test error
DIO5 16 Ready for more commands
DIO6 32 not assigned, always 0
DIO7 64 Service Request bit
DIO8 (MSB) 128 not assigned, always 0

Serial Poll Bit Description

DIO1

When enabled by the M1 command,

Input line (active transition state determined by the

DIO1

is cleared after the controller serial polls the

DIO2

DIO3

When enabled by the M2 command,
transition state determined by the
after the controller serial polls the

DIO3

is set when an invalid command is sent to the
command will enable a
received. The bit is cleared after the controller sends a
and reads the status string from the

(SRQ Bit Value if set to logic 1)

DIO1

is set by a transition on the Service

Digital488.

DIO2

is set on an

Invert

command

Digital488.

Service Request

to occur then an invalid command is

Digital488.

Invert

EDR

(I32)

).

Digital488.

Status

command

transition (active

DIO2

command

(I64)

is cleared

M4

The

(U0X)

).

DIO4

The status of

Digital488.

test fails,

DIO4

DIO4

is determined after the

If the self test passes, the

will be set to a logic 1.

Test

command

DIO4

bit will remain a zero. If the self

3.24

(T0X)

is sent to the

Section 3 Command Descriptions

The M8 command will cause a

DIO4

to
controller sends a
the

DIO5

DIO6 DIO6
DIO7

DIO8 DIO8

Example:

CLEAR 718
OUTPUT 718;"M4X"
OUTPUT 718;"F7X"

SPOLL (718)

The
processed by the
processing commands which have been received from the controller. When
used with the
when the
before the

When the
logic one. This is used by the controller to determine that the

Request

being set if the self test fails. The

Digital488.

DIO5

is not used, and is always a logic zero.

was generated by the

is not used, and is always a logic zero.

Service Request

Status

bit is set after an entire command string has been received and

M16

DIO5

bit is set. An

DIO5

bit can be cleared.

Digital488

command

Digital488.

command, a

generates a

reset the
select SRQ on Bus error
send an invalid bus command.
ERROR and SRQ LEDs should illuminate
display should be 84 (64+16+4)

(U0X)

The bit is clear while the

Service Request

Execute

Service Request,

Digital488.

Digital488

to be generated in addition

DIO4

bit is cleared after the

and reads the status string from

Digital488

will also be generated

the

(X)

must be received

DIO7

will be set to a

Service

command

is

64 denotes the
READY for more commands. 4 denotes a Bus error.

When serial polled,the SRQ LED will turn off.

Digital488

was the source of the SRQ. 16 denotes the

3.25

Digital488

is

Section 3 Command Descriptions

Status Un

Status

The
next addressed to talk. The status of the
interfering with normal operation. Any error conditions are cleared after the status string is
read by the controller. The
bit from the I/O ports

U0

Un

The format of the status byte returned by the
is as follows:

*.*C#E#F#G#I###K#M###P#R#Y#

where each # equals the number corresponding to that command. The leading
information

Example:

DIM A$[50]
CLEAR 718
OUTPUT 718;"U0X"
ENTER 718; A$
DISP A$

command (U0) will cause the

Status

command (Un) also enables the controller to read any single

(U1

through

Send the
Send the status of bit n (1 thru 40) when next addressed to talk

*.*

Digital488

is the revision level of the

U40).

status when next addressed to talk

dimension A$
reset the
send U0 to the
read the status byte
display =

1.0C0E0F0G0I000K0M000P0R0Y0

Digital488

Digital488

Digital488

Digital488

Digital488

Digital488

to send the status messag e when

may be read at any time without

after receiving a

firmware.

U0

command

The status returned after receiving a
depending on the level of the line, and the state of the

CLEAR 718
OUTPUT 718;"U22X"
ENTER 718;A$
DISP A$

U1

through

reset the
request the status of bit 22
read the status bit
display shows a 0 (dependent on the signal
applied to the input

U40

Digital488

is an ASCII character '1' or '0',

Invert

3.26

command (

I16).

Section 3 Command Descriptions

Below is a summary of the

C# Configuration
C0

All ports are inputs

C1

Port 1 is an output, ports 2 thru 5 are inputs

C2

Ports 1 and 2 are outputs, ports 3 thru 5 are inputs

C3
C4
C5

All ports are outputs

E# Error Message
0
1
2
3
4
5

F# Data Format
F0

Hexadecimal

F1

ASCII

F2

Binary

F3

Decimal

F4

Ports 1 thru 3 are outputs, ports 4 and 5 are inputs
Ports 1 thru 4 are outputs, port 5 is an input

No error
Unrecognized command (ex. W3)
Illegal command option (ex. F8)
Conflict (attempt to output data to an input port)
ROM error
RAM error

High Speed Binary

Status (U0

) information.

I### Invert Control Lines
I0

All contr o l and data lines are active high

I1
I2
I4
I8 Clear
I16 Data
I32 EDR
I64 Service

Note: the status indication reflects the sum of all received

Inhibit

output is active low

Trigger
Data Strobe

output is active low

output is active low

output is active low
is active low
input is fallling edge sensitive

input is falling edge sensitive

3.27

Invert

commands.

Section 3 Command Descriptions

K# End Or Identify
K0
K1

M## Service Request
M0
M1
M2
M4
M8
M16

Note: the status indication reflects the sum of all received

P# Selected Port
P0

All por ts selected

P1

Port 1 selected

P2
P3

Port 3 selected

P4

Port 4 selected

P5
R# Data Ready

R0

Data is not latched, but is read when Digital 488 is

addressed to talk

R1

Data is latched on

EOI enabled
EOI disabled

SRQ is disabled
SRQ on
SRQ on
SRQ on Bus error
SRQ on Test error
SRQ on Ready

Port 2 selected

Port 5 selected

Service

EDR

input transition

input transition

EDR

transition

Service Request

commands.

T# Test LED
T0

Y# Terminator
Y0

CR LF

Y1

LF CR

Y2

CR only

Y3

LF only

Perform RAM and ROM test

3.28

Section 3 Command Descriptions

Terminator Yn

The IEEE 488 bus terminator defaults at power-on to the settings on Switch S1 It

also may be programmed for any combination of Carriage Return (CR) and Line Feed (LF).

Y0

The
sequence to send LF-CR. Y2 sends CR only and

Example:

CLEAR 718
OUTPUT 718;"Y3X"

mode is the most commonly accepted terminator, CR-LF. Y1 reverses the

Y3

sends LF only.

Y0

CR LF

Y1

LF CR

Y2

CR only

Y3

LF only

select line feed terminator

3.29

Section 3 Command Descriptions

Test T0

Test

The

command is used to verify hardware and LED operation.

T0

The T0 command will cause the
test is successful, all LEDs will flash for one-half second. If a test fails, the
LED will remain illuminated. Use the
self test error.

Example:

CLEAR 718
OUTPUT 718;"T0X"

Perform RAM and ROM test

Digital488

Status

reset the Digital488
send self test command

to initiate a ROM/RAM test. If the

command to determine the cause of the

Error

3.30

Section 4 IEEE 488 Primer

IEEE 488 Primer

4.1 HISTORY

IEEE 488

The
Electronic Engineers in 1975 and revised in 1978. The
designated

computer interfaces. This placed the burden of system hardware design on the end user. If his application required
the products of several different manufacturers, then he might need to design several different hardware and
software interfaces. The popularity of the

B

us or
and control protocols. The use of the
the interface to design of the high level software that is specific to the measurement application.

IEEE 488-1978

Prior to the adoption of this standard, most instrumentation manufacturers offered their own versions of

GPIB

) is due to the total specification of the electrical and mechanical interface as well as the data transfer

4.2 GENERAL STRUCTURE

bus is an instrumentation communication bus adopted by the Institute of Electrical and

Digital488

.

IEEE 488

IEEE 488

interface (sometimes called the General Purpose Interface

standard has moved the responsibility of the user from design of

conforms to this most recent revision

The main purpose of the
either be an instrument or a computer. Before any information transfer can take place, it is first necessary to
specify which will do the talking (send data) and which devices will be allowed to listen (receive data). The
decision of who will talk and who will listen usually falls o n the

Active Controller

System Controller

The
speak at a time and the chairman is responsible for recognizing members and allowing them to have their say. On
the bus, the device which is recognized to speak is the
information transferred is to be clearly understood by all. The act of "giving the floor" to that device is called

Addressing to Talk

he can appoint an acting chairman to take control of the proceedings. For the

Active Controller

.

is similar to a committee chairman. On a well run committee, only one person may

. If the committee chairman can not attend the meeting, or if other matters require his attention,

.

GPIB

is to transfer information between two or more devices. A device can

Active Talker

4.1

System Controller

. There can only be one Talker at a time if the

which is, at power on, the

GPIB

, this device becomes the

Section 4 IEEE 488 Primer

At a committee meeting, everyone present usually listens. This is not the case
with the
commands all other devices to ignore what is being transmitted. A device is instructed
to listen by being

Listener

GPIB

. The

. Devices which are to ignore the data message are instructed to

Active Controller

Addressed to Listen

selects which devices will listen and

. This device is then referred to as an

Unlisten

Active

.

The reason some devices are instructed to
college instructor is presenting the day's lesson. Each student is told to raise their
hand if the instructor has exceeded their ability to keep up while taking notes. If a
hand is raised, the instructor stops his discussion to allow the slower students the time
to catch up. In this way, the instructor is certain that each and every student receives
all the information he is trying to present. Since there are a lot of students in the
classroom, this exchange of information can be very slow. In fact, the rate of
information transfer is no faster than the rate at which the slowest note-taker can keep
up. The instructor, though, may have a message for one particular student. The
instructor tells the rest of the class to ignore this messag e (
one student at a rate which he can understand. This information transfer can then
happen much quicker, because it need not wait for the slowest student.

GPIB

The

called

For data transfer on the

a)
b) Designate who will
c) Designate all the devices who are to

devices to

d) Indicate to all devices that the data transfer can take place.

transfers information in a similar way. This method of data tr ansfer is

handshaking

Unlisten

. More on this later.

IEEE 488

all devices to protect against eavesdroppers.

talk

by

listen

.

Active Controller

, the

addressing

Unlisten

a device to

listen

by

is quite simple. Suppose a

Unlisten

must …

talk

addressing

) and tells it to that

.

those

4.2

Section 4 IEEE 488 Primer

4.3

Section 4 IEEE 488 Primer

4.3 SEND IT TO MY ADDRESS

In the previous discussion, the terms

to Listen

one system. Each of these devices must have a unique address to avoid confusion. In a
similar fashion, every building in town has a unique address to prevent one home from
receiving another home's mail. Exactly how each device's address is set is specific to the
product's manufacturer. Some are set by DIP switches in hardware, others by software.
Consult the manufacturer's instructions to determine how to set the address.

Controller

(MTA),

were used. These terms require some clarification.

IEEE 488

The

Addresses are sent with

. These commands include

Talk Address Group

standard permits up to 15 devices to be configured within

universal (multiline

My Listen Address

(TAG), and

Listen Address Group

Addressed to Talk

) commands from the

(MLA),

(LAG).

Addressed

and

Active

My Talk Address

4.4 BUS MANAGEMENT LINES

Five hardware lines on the
on these lines are often referred to as
active low, i.e. a low voltage represents a logic "1" (asserted), and a high voltage
represents a logic "0" (unasserted).

GPIB

are used for bus management. Signals

uniline

(single line) commands. The signals are

4.4.1 Attention (ATN)

ATN

is one of the most important lines for bus management. If Attention
is asserted, then the information contained on the data lines is to be in terpreted as a
multiline command. If it is not, then that information is to be interpreted as d ata for

Active Listener

the
of this line.

s. The

Active Controller

is the only bus device that has control

4.4

Section 4 IEEE 488 Primer

4.4.2 Interface Clear (IFC)

IFC

The
bus devices in a known state. Although device configurations vary, the
command usually places the devices in the Talk and Listen Idle states (neither

Talker

nor

line is used only by the

Active Listener

).

System Controller

. It is used to place all

IFC

4.4.3 Remote Enable (REN)

When the
respond to remote operation. Generally, the
any bus programming is attempted. Only the

Remote Enable

System Controller

line.

sends the

REN

command, bus devices will

REN

command should be issued before

System Controller

has control of the

4.4.4 End or Identify (EOI)

EOI

The
device that is sending the data asserts

EOI

The
some special character such as carriage return.

The
simultaneously asserting

line is used to signal the last byte of a multibyte data transfer. The

EOI

during the transfer of the last data byte.

signal is not always necessary as the end of the data may be indicated by

Active Controller

EOI

also uses
and

ATN

EOI

to perform a

.

Parallel Poll

by

4.4.5 Service Request (SRQ)

When a device desires the immediate attention of the

SRQ

asserts
requested service. This is accomplished with a

. It is then the Controller's responsib ility to determine which device

Serial Poll

Active Controller

Parallel Poll

or a

Active

it

.

4.5

Section 4 IEEE 488 Primer

4.5 HANDSHAKE LINES

GPIB

The
got it" sequence. This handshake protocol assures reliable data transfer, at the rate
determined by the slowest Listener. One line is controlled by th e Talker, while the
other two are shared by all Active Listeners. The handshake lines, like the other

IEEE 488

lines, are active low.

uses three handshake lines in an "I'm ready - Here's the data - I've

4.5.1 Data Valid (DAV)

DAV

The

NDAC

is asserted (active low) which indicates that all Listeners have accepted
the previous data byte transferred. The
waits until
Listeners are ready to accept the information. When
the proper state, the
on the bus is valid.

NRFD

line is controlled by the

Talker

is unasserted (high) which indicates that all Addressed

Talker

asserts

DAV

( active low) to indicate that the data

Talker

then outputs data on the bus and

NRFD

. The

Talker

and

verifies that

NDAC

are in

4.5.2 Not Ready for Data (NRFD)

This line is used by the
are ready to accept new data. The
unassert this line (high) which they will do at their own r a te wh en they are r eady
for more data. This assures that all devices that are to accept the information are
ready to receive it.

Listeners

Talker

must wait for each

to inform the

Talker

Listener

when they

to

4.5.3 Not Data Accepted (NDAC)

NDAC

The
indicates to the
information. Each device releases
will not go high until the slowest Listener has accepted the data byte.

Talker

line is also controlled by the

that each device addressed to listen has accepted the

NDAC

(high) at its own rate, but the

Listeners

. This line

NDAC

4.6

Section 4 IEEE 488 Primer

4.6 DATA LINES

GPIB

The
These eight data lines use the convention of
binary designation of D0 to D7. The data lines are bidirectional and are active low.

provides eight data lines for a bit parallel/byte serial data tr ansfer.

DIO1

through

DIO8

instead of the

4.7 MULTILINE COMMANDS

Multiline

bus with
listen, Untalk and Unlisten.

ATN

(bus) commands are sent by the

asserted. These commands include addressing commands for talk,

4.7.1 Go To Local (GTL)

This command allows the selected devices to be manually controlled.

($01)

Active Controller

4.7

over the data

Section 4 IEEE 488 Primer

4.7.2 Listen Address Group (LAG)

There are 31 (0 to 30) listen addresses associated with this group. The 3
most significant bits of the data bus are set to 001 while the 5 least significant
bits are the address of the device being told to listen.

4.7.3 Unlisten (UNL)

This command tells all bus devices to Unlisten. The same as
Unaddressed to Listen. ($3F)

4.7.4 Talk Address Group (TAG)

There are 31 (0 to 30) talk addresses associated with this group. The 3
most significant bits of the data bus are set to 010 while the 5 least significant
bits are the address of the device being told to talk.

4.7.5 Untalk (UNT)

This command tells bus devices to Untalk. The same as Unaddressed to
Talk. ($5F)

4.7.6 Local Lockout (LLO)

Issuing the
functions. ($11)

LLO

command prevents manual control of the instrument's

4.7.7 Device Clear (DCL)

This command causes all bus devices to be initialized to a
pre-defined or power up state. ($14)

4.8

Section 4 IEEE 488 Primer

4.7.8 Selected Device Clear (SDC)

This causes a single device to be initialized to a pre-defined or power up
state. ($04)

4.7.9 Serial Poll Disable (SPD)

SPD

The
status byte. ($19)

command disables all devices from sending their Serial Poll

4.7.10 Serial Poll Enable (SPE

A device which is Addressed to Talk will output its Serial Poll status
byte after

SPE

is sent and

ATN

)

is unasserted. ($18)

4.7.11 Group Execute Trigger (GET)

This command usually signals a group of devices to begin executing a
triggered action. This allows actions of different devices to begin
simultaneously. ($08)

4.7.12 Take Control (TCT)

This command passes bus control respon sib ilities from the current

Controller

to another device which has the ability to control. ($09)

4.7.13 Secondary Command Group (SCG)

These are any one of the 32 possible commands (0 to 31) in this group.
They must immediately follow a talk or listen address. ($60 to $7F)

4.9

Section 4 IEEE 488 Primer

4.7.14 Parallel Poll Configure (PPC)

This configures devices capable of performing a
which data bit they are to assert in response to a

Parallel Poll

Parallel Poll

as to

. ($05)

4.7.15 Parallel Poll Unconfigure (PPU)

This disables all devices from responding to a

Parallel Poll

. ($15)

4.8 MORE ON SERVICE REQUESTS

Most of the commands covered, both uniline and multiline, are the
responsibility of the
Most of these happen routinely by the interface and are totally transparent to the
system programmer. Other commands are used directly by the user to provide
optimum system control. Of the uniline commands,
test system and the software designer has easy access to this line by most devices.
Service Request is the method by which a bus device can signal to the
that an event has occurred. It is similar to an interrupt in a microprocesso r based
system.

Most intelligent bus peripherals have the ability to assert
might assert it when its measurement is comp lete, if its input is overloaded or for any
of an assortment of reasons. A power supply might
limited. This is a powerful bus feature that removes the burden from the

Controller

says, "Do what I told you to do and let me know when you're done" or "Tell me
when something is wrong."

to periodically inquire, "Are you done yet?". Instead, the

Active Controller

to send and the bus devices to recognize.

SRQ

is very important to the

Controller

SRQ

. A DMM

SRQ

if its output has current

System

Controller

SRQ

Since
determine which device requested the service without additional information. This
information is provided by the multiline commands for

is a single line command, there is no way for the

Serial Poll

4.10

Controller

Parallel Poll

and

to

.

Section 4 IEEE 488 Primer

4.8.1 Serial Poll

Suppose the

let's assume there are several devices which could assert

Controller

sequentially. If any device responds with DIO7 asserted it indicates to the

Controller

bits will indicate why the device wanted service. This

sequence, and any resulting action, is under control of the software designer.

issues an

that it was the device that asserted

Controller

SPE

receives a service request. For this example,

(Serial Poll enable) command to each device

SRQ

. Often times the other

Serial Polling

4.8.2 Parallel Poll

Parallel Poll

The
device requested service. It provides the who but not necessarily the why.
When bus devices are configured for Parallel Poll, they are assigned one bit
on the data bus for their response. By using the Status bit, the logic level of
the response can be programmed to allow logical OR/AND conditions on
one data line by more than one device. When

Controller

must then analyze the eight bits of data received to determine the source of
the request. Once the source is determined, a
determine the why.

Of the two polling types, the

to determine the who and why. In addition, most devices support

(under user's software) conducts a

is another way the

Serial Poll

Controller

SRQ

Parallel Poll

Serial Poll

is the most popular due to its ability

can determine which

is asserted, the

SRQ

. The

Controller

. The

might be used to

Serial Poll

only.

4.11

Section 5 Service Information

Service Information

5.1 Factory Service

IOtech

maintains a factory service center in Cleveland, Ohio. If problems are
encountered in using the
problems can be resolved by discussing the problems with our applications department. If
the problem cannot be solved by this method, you will be instructed as to the proper return
procedure.

5.2 Theory of Operation

Digital488

you should first telephone the factory. Many

The Heart of the
bytes of firmware EPROM [U102 (2764)] and 8K bytes of static RAM [U103 (6264)]. A
Versatile Interface Adapter [U104 (65B22)] is used to generate real-time interrupts for the
firmware operating system. The front panel annunciators are also driven by U104 through
an inverter [U113 (74LS04)].

The IEEE 488 bus interface is accomplished by a TMS9914A [U106] controller
with drivers U107 and U108. The digital I/O ports are controlled by 'PIA's [U202-U204
(68B21)]. SW1 is read through one port of U204.

Power is supplied by an external unregulated 9 volt wall mount supply. Regulation
to the required +5 volts is provided by U109 [7805]. Decoding of the microprocessor
address space is accomplished with a Programmable Logic Array [U110 (16L8)]. The
Memory space allocation is...

Address Device

$6000-$7FFF U103 6264 Static RAM
$9200-$9204 U202 6821 Digital I/O
$9400-$9404 U203 6821 Digital I/O
$9800-$9804 U204 6821 Digital I/O
$A000-$A007 U106 TMS9914A IEEE Controller
$B000-$B00F U104 R65C22 VIA
$E000-$FFFF U102 2764 Programmed EPROM

Digital488

is a 6809 microprocessor [U101] supported by 8K

Part Number Function

5.1

Section 5 Service Information

5.6 Digital488 Replaceable Parts List

Schematic Part Number Description

C101-C108 C-5-.1 Ceramic, 25v
C110,C113 C-5-.1 Ceramic, 25v
C117,C118 C-5-15p Ceramic, 25v
C124 C-2-10 Electrolytic, 25v
C201-C205 C-5-.1 Ceramic, 25v
C123 C-5-1 Ceramic, 25v
D101 RF-1 Small Signal Diode
D102-D106 DD-2 Red PC Mount
J101 CN-2 IEEE 488 Connector
R101 R-1-68K 68K½, 1/4w carbon
R102 RN-4-4.7K 4.7K½ x 7 SIP
R104 RN-2-470 470½ x 5 SIP
R105 R-2-39 39½, 1w carbon
R201-R202 R-1-1K 1K½, 1/4w carbon
R206 R-1-1K 1K½, 1/4w carbon
S201 SW-6-8 8 Pole DIP
U102 Digital488-600 Programmed EPROM
U103 IC-41 6264-15 8K x 8 CMOS SRAM
U104 IC-23 65B22 Versitile Interface Adapter
U106 IC-3 TMS9914ANL IEEE Controller
U107 IC-4 SN75160BN IEEE Driver
U108 IC-5 SN75162BN IEEE Driver
U110 Digital488-601 Programming Equation - 16L8 PAL
U113 IC-33 74LS04 Hex Inverter
U109 IC-30 LM7805CT Regulator - +5v
U201 IC-1 MC68B09P Microprocessor
U202-U204 IC-2 68B21 PIA
U205 IC-47 74LS05
U206 IC-32 74LS375
Y101 CR-5 8.0000 MHz Crystal

5.5

Section 5 Service Information

5.7 Digital488OEM Replaceable Parts List

Schematic Part Number Description

C101-C112 C-5-.1 Ceramic, 25v
C113 C-5-1 Ceramic, 25v
C114,C115 C-5-15p Ceramic, 25v
C116 C-2-10 Electrolytic, 25v
D101 RF-1 Small Signal Diode
D102-D106 DD-2 Red PC Mount
J101 CN-2 IEEE 488 Connector
J102 CN-5-12 12 x 2 0.1" Header
J103 CN-5-25 25 x 2 0.1" Header
J104 CN-32-2 2 position Mate-N-Loc Socket
R101 R-1-68K 68K½, 1/4w carbon
R102 RN-4-4.7K 4.7K½ x 7 SIP
R103 RN-2-470 470½ x 5 SIP
S101 SW-6-8 8 Pole DIP
U101 IC-1 MC68B09P Microprocessor
U102 Digital488-600 Programmed EPROM
U103 IC-41 6264-15 8K x 8 CMOS SRAM
U104 IC-23 6 5 B22 Versitile Interface Adapter
U105 Digital488-601 Programming Equation - 16L8 PAL
U106 IC-3 TMS9914ANL IEEE Controller
U107 IC-4 SN75160BN IEEE Driver
U108 IC-5 SN75162BN IEEE Driver
U109 IC-33 74LS04 Hex Inverter
U110-U112 IC-2 68B21 PIA
Y101 CR-5 8 .0000 MHz Crystal

5.6

Appendix A Digital488 Command Summary

Command Code Description

Bit Set An

Set bit n (1 thru 40)

Bit Clear Bn

Bus Output G0

G1
G2

Configure C0

C1
C2
C3
C4
C5

Data Dn..Z

Data Ready R0

R1

EOI K0

K1

Execute X

Format F0

F1
F2
F3
F4
F5

Clear bit n (1 thru 40)

Input and Output port data sent on talk
Only Input por t data sent on talk
Only Output port data sent on talk

All ports are inputs
Port 1 is an output, ports 2 thru 5 are inputs
Ports 1 and 2 are outputs, ports 3 thru 5 are inputs
Ports 1 thru 3 are outputs, ports 4 and 5 are inputs
Ports 1 thru 4 are outputs, port 5 is an input
All ports are output s

Data to be outputted is entered after "D" and
terminated by "Z"

Data is read when system is addressed to talk
Data is latched on EDR transition

EOI enabled
EOI disabled

Execute preceeding command string

ASCII Hexadecimal
ASCII Character
ASCII Binary
ASCII Decimal
Binary
High Speed Binary

Handshake H0

H1
H2

Pulse the Clear line
Pulse the Strobe line
Pulse the Trigger line

A.1

Appendix A Digital488 Command Summary

Command Code Description

Inhibit Q0

Q1

Clear Inhibit line
Set Inhibit line

Invert I0

I1
I2
I4
I8
I16
I32
I64

Port P0

P1
P2
P3
P4
P5

SRQ Mask M0

M1
M2
M4
M8
M16

Status U0

Un

Terminator Y0

Y1
Y2
Y3

All control line output s are active high
Inhibit output is active low
Trigger output is active low
Data Strobe output is active low
Clear output is active low
Data is low true
EDR input is falling-e dg e se ns itive
Service input is falling-edge sensitive

All ports selected
Port 1 selected
Port 2 selected
Port 3 selected
Port 4 selected
Port 5 selected

SRQ is disabled
SRQ on Service Input transition
SRQ on EDR input transition
SRQ on Bus error
SRQ on Self-test error
SRQ on Ready

Send Status information when next addressed to
talk (*.*C#E#F#G#I###K#M###P#R#Y#)
Read state of bit n (1 thru 40 )

CR LF
LF CR
CR only
LF only

Test T0

Perform RAM and ROM test

A.2