IOtech 488 schematic
Digital488 and Digital488/32/OEM
IEEE 488 to Digital I/O Interface
IOtech, Inc.
25971 Cannon Road
Cleveland, OH 44146-1833
Phone: (440) 439-4091
Fax: (440) 439-4093
E-mail (Product Information): sales@iotech.com
E-mail (Technical Support): productsupport@iotech.com
Internet: www.iotech.com
Digital488 and
Digital488/32/OEM
IEEE488 to Digital I/O Interface
p/n 110-0901 Rev 6.0
© 1990… 2004 by IOtech, Inc. 916895 Printed in the United States of America.
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: (440) 439-4091, fax: (440) 439-4093, e-mail: sales@iotech.com
Limitation of Liability
IOtech, Inc. cannot be held liable for any damages resulting from the use or misuse of this product.
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may only be used on one installation. You may make archival backup copies.
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 in ways other than described in this manual can present serious safety hazards or cause equipment
damage.
This warning symbol is used in this manual or on the equipment to warn of possible injury or death from electrical
shock under noted conditions.
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.
This symbol indicates the message is important, but is not of a Warning or Caution category. These notes can be of
great benefit to the user, and should be read.
In this manual, the book symbol always precedes the words “Reference Note.” This type of note identifies the location
of additional information that may prove helpful. References may be made to other chapters or other documentation.
Tips provide advice that may save time during a procedure, or help to clarify an issue. Tips may include additional
reference.
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 been an ISO 9001 registered firm 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.
Table of Contents
1 - Introduction
General Description …… 1-1
Digital488 …… 1-1
Digital488/32/OEM …… 1-1
Available Accessories …… 1-2
Specifications …… 1-2
Digital488 Specifications …… 1-2
Digital I/O …… 1-2
IEEE 488 …… 1-3
General …… 1-3
Digital488/32/OEM Specifications …… 1-4
Digital I/O …… 1-4
IEEE 488 …… 1-4
General …… 1-5
Abbreviations …… 1-6
2 - Getting Started
Inspection …… 2-1
Configuration …… 2-1
IEEE 488 Address Selection …… 2-2
IEEE 488 Bus Output Terminator
Selection ……2-3
Digital Input/Output Ports …… 2-3
Logic Levels …… 2-3
Digital I/O Port Pin Outs …… 2-4
Control Lines …… 2-5
Clear …… 2-5
Data Strobe …… 2-5
External Data Ready [EDR] …… 2-6
Inhibit …… 2-6
Trigger …… 2-6
Service …… 2-7
IEEE 488 Bus Implementation …… 2-7
My Talk Address (MTA) …… 2-7
My Listen Address (MLA) …… 2-8
Device Clear (DCL and SDC) …… 2-8
Group Execute Trigger (GET) …… 2-8
Interface Clear (IFC) …… 2-8
Serial Poll Enable (SPE) …… 2-8
Serial Poll Disable (SPD) …… 2-8
Unlisten (UNL) …… 2-8
Untalk (UNT) …… 2-8
Installation …… 2-9
3 - Command Descriptions
Bit Set An …… 3-1
Bit Clear Bn …… 3-1
Bus Input/Output Gn …… 3-2
Configure Cn …… 3-2
Data Dn....Z …… 3-3
Data Ready Rn …… 3-4
End or Identify (EOI) Kn …… 3-4
Execute X …… 3-5
Format Fn …… 3-5
F0 Format- ASCII Hexadecimal …… 3-5
F1 Format - ASCII Character …… 3-6
F2 Format - ASCII Binary …… 3-7
F3 Format - ASCII Decimal …… 3-7
F4 Format - Binary …… 3-8
F5 Format - High Speed Binary …… 3-8
Handshake Hn …… 3-9
Inhibit Qn …… 3-9
Invert In …… 3-9
Port Pn …… 3-10
Service Request Mask (SRQ) Mn …… 3-10
Serial Poll Status Byte …… 3-11
Status Un …… 3-12
Terminator Yn …… 3-14
Test T0 …… 3-15
DaqBook/DaqBoard/Daq PC-Card User’s Manual 916895 Index-i
4 - IEEE 488 Primer
History …… 4-1
General Structure …… 4-1
Send It To My Address …… 4-3
Bus Management Lines …… 4-3
Attention (ATN) …… 4-3
Interface Clear (IFC) …… 4-3
Remote Enable (REN) …… 4-3
End or Identify (EOI) …… 4-3
Service Request (SRQ) …… 4-3
Handshake Lines …… 4-4
Data Valid (DAV) …… 4-4
Not Ready for Data (NRFD) …… 4-4
Not Data Accepted (NDAC) …… 4-4
Data Lines …… 4-4
Multiline Commands …… 4-5
Go To Local (GTL) …… 4-5
Listen Address Group (LAG) …… 4-5
Unlisten (UNL) …… 4-5
Talk Address Group (TAG) …… 4- 5
Untalk (UNT) …… 4-5
Local Lockout (LLO) …… 4-5
Device Clear (DCL) …… 4-5
Selected Device Clear (SDC) …… 4-5
Serial Poll Disable (SPD) …… 4-5
Serial Poll Enable (SPE) …… 4-5
Group Execute Trigger (GET) …… 4-5
Take Control (TCT) …… 4-5
Secondary Command Group (SCG) …… 4-5
Parallel Poll Configure (PPC) …… 4-6
Parallel Poll Unconfigure (PPU) …… 4-6
More On Service Requests …… 4-6
Serial Poll …… 4-6
Parallel Poll …… 4-6
5 - Service Information
Factory Service …… 5-1
Theory of Operation …… 5-1
Digital488 Mother Board …… 5-2
Digital488 I/O Board …… 5-4
Digital488/32/OEM …… 5-5
Digital488/OEM …… 5-6
Appendix A Digital488 Command Summary
Appendix B IEEE Command and Address
Messages
Appendix C Digital488/OEM Mechanical
Dimensions
ii 916895 DBK Option Cards & Modules User’s Manual
Introduction 1
General Description
Digital488
The Digital488/32/OEM is a board level interface with the same capabilities as the Digital488.
All descriptions in this manual refer to both products unless otherwise stated. When the model number
Digital488 is used in this manual, Digital488/32/OEM is also implied.
The Digital488 is a digital input and output interface to the IEEE 488 bus. 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 Digital488 has several features, which give it versatile interface 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 prog rammable, including ASCII hexadecimal,
ASCII character, ASCII binary, binary, hig h 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.
A status mode enables the controller to interrogate the programmed status of the Digital488 at any time. A
self-test is initiated at power-on which checks for proper RAM and ROM operation.
When addressed to talk, the Digital 488 will output data from all forty bits or 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.
Digital488/32/OEM
The Digital488/32/OEM is a 4 in. by 4 in., 32 I/O line interface board for transferring data between the
IEEE 488 (GBIP, HP-IP) bus and devices equipped with up to 32-bit wide digital ports.
The Digital488/32/OEM’s 32 TTL-level digital I/O lines are programmable in 4-bit ports as either inputs
or outputs. When addressed to talk, the Digital488/32/OEM will output data from all thirty-two bits or a
selected 8 bit port. The board also offers six handshake lines for implementing clear, data strobe, external
data ready, inhibit, trigger, and SRQ functions. Its firmware includes a complete command set for
facilitating the implementation of all its functions. This command set is identical to that employed by the
other board-level and external interfaces in IOtech’s industry-standard Digital488 family, facilitating quick
prototyping and making the Digital488/32/OEM compatible with other Digital488 family units.
Digital488 User’s Manual 11-28-01 Introduction, 1-1
Available Accessories
Additional accessories that can be ordered for the Digital488 include:
CA-7-1 1.5 foot IEEE 488 Cable
CA-7-2 6 foot IEEE 488 Cable
CA-7-3 6 foot shielded IEEE 488 Cable
CA-7-4 6 foot reverse entry IEEE 488 Cable
CA-8-50† 6 foot, 50-conductor ribbon cable with a card edge
CA-46-40 6 foot digital I/O header connector to ribbon cable for the
CN-6-50† 50 Pin solder tab edge connector.
CN-20 Right Angle IEEE 488 adapter, male and female
CN-22 IEEE 488 Multi-tap bus strip, four female connectors in parallel
CN-23 IEEE 488 panel mount feed-through connector, male
and female
Rack488-3† 5-1/4" by 19" rack mount for one Digital488
connector on one end, the other end un-terminated.
Digital488/32/OEM
Rack488-4† 5-1/4" by 19" rack mount for two Digital488s
TR-2† 110 volt Wall mount power supply for the Digital488
TR-2E† 220 volt Wall mount power supply for the Digital488
TR-5 110 volt Wall mount power supply for the Digital488OEM
TR-5E 220 volt Wall mount power supply for the Digital488OEM
†
For use with Digital488 Only
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).
1-2, Introduction 11-28-01 Digital488 User’s Manual
IEEE 488
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.
Terminal Installation Category:
Standard: Not Applicable. CE: Category 1 for all terminals.
Dimensions:
188 mm deep x 140 mm wide x 68 mm high (7.39" x 5.5" x 2.68").
Weight: 1.55 kg. (3.6 lbs).
Operating Environment:
Standard: Indoor, 0° to 50°C; 0 to 70% RH to 35°C. Linearly derate 3% RH/°C from 35 to 50°C.
CE: Indoor use at altitudes below 2000 meters, 0° to 40°C; 80% maximum RH up to 31°C decreasing
linearly 4% 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.
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.
CAUTION
WARNING
Digital488 User’s Manual 11-28-01 Introduction, 1-3
Do not connect AC power line directly to the Digital488. Direct AC connection will
damage equipment.
CAUTION
Digital488/32/OEM Specifications
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.
Never disassemble the interface case while it is connected to the AC power line.
Internal voltage potentials exist which could cause bodily injury or death.
Digital I/O
Configuration:
Four 8-bit ports, programmable as inputs o r outputs.
Transistor-Transistor Logic (TTL) Levels:
Outputs will drive 2 TTL loads.
Connector:
One 40 pin header, organized as two rows of 20 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.
WARNING
CAUTION
1-4, Introduction 11-28-01 Digital488 User’s Manual
General
Configuration:
Four 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:
101.6mm square x 16.51mm high (4” square x 0.65” high)
Weight: 0.13 kg. (0.29 lbs).
Operating Environment:
Standard: Indoor, 0° to 50°C; 0 to 70% RH to 35°C. Linearly derate 3% RH/°C from 35 to 50 °C.
Controls:
IEEE parameter switches.
Indicators:
On-board and 10 pin header for remote use. The external LEDs are connected to VCC through a
resistor network. The pin-out table for the LED status header is located in Figure 1.1.
PIN #
LED CONNECTOR
1 Error (Cathode)
2 Error (Anode)
3 SRQ (Cathode)
4 SRQ (Anode)
5 Listen (Cathode)
6 Listen (Anode)
7 Talk (Cathode)
8 Talk (Anode)
9 Power (Cathode)
10 Power (Anode)
Figure 1.1: LED Indicators
Power:
User supplied +5 volts ±0.25% at 1 amp. Mating power connector with 8-inch leads provid ed.
WARNING
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.
CAUTION
Digital488 User’s Manual 11-28-01 Introduction, 1-5
Never disassemble the interface case while it is connected to the AC power line.
Internal voltage potentials exist which could cause bodily injury or death.
Abbreviations
The following IEEE 488 abbreviations are used throughout this manual.
addr n IEEE bus address "n"
ATN Attention line
CA Controller Active
CR Carriage 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 Enable
SRQ Service Request
TA Talker Active
TAD Talker Address
TCT Take Control
term Terminator
UNL Unlisten
UNT Untalk
* Unasserted
1-6, Introduction 11-28-01 Digital488 User’s Manual
Getting Started 2
Inspection
The unit was carefully inspected, both mechanically and electrically, 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 materials in the event that
shipment back to the factory becomes necessary.
Every Digital488 is shipped with the following....
• Digital488 IEEE Digital I/O Converter
• CN-8-50 Digital I/O Port Mating Connector
• Digital488 User’s Manual
• Power Supply TR-2; 115V or
• TR-2E; 220V
Every Digital488/32/OEM is shipped with the following....
• Digital488/32/OEM IEEE Digital I/O Converter
• Digital488 User’s Manual
• CA-106 1 foot ribbon cable to IEEE488 connector
• Macro488OEM-002 Power Plug Assembly
Configuration
The Digital488 has one internal 8 position switch which determines 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 factory default setting for SW1.
To modify any of these defaults, follow this simple procedure. Disconnect the power supply fr om the AC
line and from the interface. Disconnect any IEEE or digital I/O cables prior to disassembly.
SW1 Factory Default Settings
Digital488 User’s Manual 11-19-01 Getting Started, 2-1
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 screws into the rear panel.
IEEE 488 Address Selection
The IEEE 488 bus address is set by SW1-1 through SW1-5. The address can be set from 0 through 30 and
is read only at power on. The address is selected by simple binary weighting with SW1-1 being the least
significant bit and SW1-5 the most significant bit. The factory default is address 18.
If address 31 is selected, it defaults to address 30 because the IEEE 488 standard has reserved address 31.
WARNING
SW1 View for IEEE Bus Address Selection
2-2, Getting Started 11-19-01 Digital488 User’s Manual
IEEE 488 Bus Output Terminator Selection
The terminating characters sent on output by the Digital488 are determined by SW1-6 through SW1-8.
The terminator switches are read 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
again default to the switch settings. The factory default settings are Carriage Return - Line Feed with EOI
asserted.
The Digital488 ignores all terminators received from the bus controller. Only the Execute command (X)
is used to signal the Digital488 that a command string has been completed.
Digital Input/Output Ports
The Digital488 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.
The Digital488/32/OEM has 32 data lines, which can be programmed in groups of 8 as either input
or output. Each 8 bit group is one port, beginning with Port 1 as the least significant 8 bits,
and Port 4 as the most significant 8 bits.
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 voltage s to -0.3 to +7.0 volts.
All I/O lines are referenced to COMMON (Pin 50).
SW1 View for Terminator Selection
Digital488 User’s Manual 11-19-01 Getting Started, 2-3
Digital I/O Port Pin Outs
The following diagram illustrates the digital I/O edge connector as view from the rear of the Digital488 and
the top PC Board edge view of the Digital488/32/OEM.
Digital488 Rear Panel I/O Connector Pin Out Digital488/32/OEM I/O Connector Pin Out
Pin Digital488
1 thru 8
Least Significant Port
9 thru 16
17 thru 24
25 thru 32
33 thru 40
Most Significant Port
Description
DATA PORT1 (Input or Output).
Pin 1 is bit 1 (LSB), Pin 8 is bit 8 (MSB).
DATA PORT2 (Input or Output)
Pin 9 is bit 1 (LSB), Pin 16 is bit 8 (MSB)
DATA PORT3 (Input or Output)
Pin 17 is bit 1 (LSB), Pin 24 is bit 8 (MSB)
DATA PORT4 (Input or Output)
Pin 25 is bit 1 (LSB), Pin 32 is bit 8 (MSB)
DATA PORT5 (Input or Output
Pin 33 is bit 1 (LSB), Pin 40 is bit 8 (MSB)
Pin Digital488/32/OEM
1 thru 8
Least Significant Port
9 thru 16
17 thru 24
25 thru 32
Most Significant Port
N/A
41 CLEAR (Output) 33
42 DATA STROBE (Output) 37
43 TRIGGER (Output) 34
44 INHIBIT (Output) 38
45 SERVICE INPUT (Input). 35
46 EXTERNAL DATA READY [EDR] (Input) 36
47,48 Not used N/A
49 +5 Volts (Do not exceed 50 mA load) 39
50 I/O COMMON (Gnd) 40
2-4, Getting Started 11-19-01 Digital488 User’s Manual
Control Lines
Six 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 be independently activated with the
Handshake (Hn) command. Note that the pin numbers for the Digital488/32/OEM are different from
the pin numbers for the Digital488.
Clear (Digital488: Pin 41
The 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. The Clear line is normally active
high. The Invert command (I8) will program it active low. The Handshake command (H0) can pulse the
Clear line, independent of any I/O operations.
Data Strobe (Digital488: Pin 42
The Data Strobe output is pulse for approximately 50 microseconds after new data is output on the
I/O port. The Data Strobe line is normally active high but may be programmed active low by the Invert
command (I4). The Handshake command (H1) can pulse the Data Strobe line, independent
of an I/O operation.
Digital488/32/OEM: Pin 33)
Timing Diagram for Clear Output
Digital488/32/OEM: Pin 37)
Timing Diagram for Strobe Output
Digital488 User’s Manual 11-19-01 Getting Started, 2-5
External Data Ready [EDR] (Digital488: Pin 46
Digital488/32/OEM: Pin 36)
The External Data Ready [EDR] line is an edge sensitive input which is used to latch input data. It is used
in conjunction with the Data Ready 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 EDR line is normally rising-edge
sensitive but can be programmed with the Invert command (I32) to be falling-edge sensitive.
Refer to the following diagram for timing relationships.
When using the EDR line with the R1 command, data is not read when the Digital488 is addressed to talk
as with R0. The Digital488 will only output data when the EDR line transitions.
EDR is not functional in the high-speed binary (F5) format.
Inhibit (Digital488: Pin 44
Digital488/32/OEM: Pin38)
The 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 Invert command (I1).
The Inhibit line can be programmed independent of any I/O operations with the Inhibit command ( Qn).
Refer to the following diagram for timing relationships.
The Inhibit 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 Digital488 is addressed to talk.
On the last data-byte transfer, the data is read again with Inhibit asserted in anticipation of another data
transfer. If Inhibit is used to sequence external hardware, you should be aware that this line will pu lse N+1
times; where N is the number of total (5 byte) data transfers.
Timing Diagram for EDR Input and Inhibit Output
Trigger (Digital488: Pin 43
Digital488/32/OEM: Pin34)
The Trigger output is pulse for approximately 50 microseconds after a 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 Invert command (I2). The Handshake command (H2) can independently pulse the
Trigger line, independent of any bus activity.
Timing Diagram for Trigger Output
2-6, Getting Started 11-19-01 Digital488 User’s Manual
Service (Digital488: Pin 45
Digital488/32/OEM: Pin35)
The Service input is an edge sensitive input capable of generating a bus Service Request (SRQ).
It is enabled with the SRQ command (M1) and defaults to rising-edge sensitive. The Invert command
(I64 ) can be used to program it to be falling-edge sensitive.
IEEE 488 Bus Implementation
The Digital488 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
Digital488 does not support or respond to include:
Remote Enable (REN) Parallel Poll (PP)
Go to Local (GTL) Parallel Poll Configure (PPC)
Local Lockout (LLO) Parallel Poll Unconfigure (PPU)
Take Control (TCT) Parallel Poll Disable (PPD)
My Talk Address (MTA)
When the Digital488 is addressed to talk (R0) it asserts Inhibit, reads the data from all ports, un-asserts
Inhibit and outputs the data to the bus in the format as defined by the Fn, Pn and Gn commands.
The output bus terminators are appended to the output with the exception of the F4 and F5 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 must be re-addressed to talk to perform subsequent reads.
In the R1 mode, it will wait for the selected EDR transition before reading the data and formatting it for
output. If the EDR line has transitioned prior to being addressed to talk, the data read at the time of EDR
will be buffered for output when next addressed to talk. If EDR transitions again before the previous EDR
buffered data has been output, the Digital488 will generate an EDR Overrun error and ignore the EDR
read request. After output in the F0 through F4 formats, the Digital488
to perform subsequent buffered output of EDR captured data.
In either Rn mode, the Digital488 can send requested status (Un) without affecting the data ports
or Inhibit. After the requested status is output, the presently programmed Rn mode returns.
EDR
cannot be used to capture data in the high-speed binary format (F5). When addressed to talk in this
format it asserts Inhibit, reads the data from all ports, un-asserts Inhibit and outputs the binary data to the
bus with EOI asserted on the fifth byte. When the last data byte is transferred, the data is read again
in anticipation of another data transfer. If Inhibit is used to sequence external hardware, this line will pulse
N+1 times; where N is the number of total (5 byte) data transfers. In this format, the Digital488 does not
have to be re-addressed to talk to read the ports multiple times.
With all Fn formats, using the Digital488 the data is output in a PORT5, PORT4, PORT3, PORT2, PORT1
sequence. Using the Digital488/32/OEM the data is output in a PORT4, PORT3, PORT2, PORT1
sequence.
must be re-addressed to talk
Digital488 User’s Manual 11-19-01 Getting Started, 2-7
My Listen Address (MLA)
When the Digital488 is addressed to listen in the F0 through F4 format, it accepts characters from the
active talker and interprets these characters as commands and command parameters. These commands are
explained in Chapter 3.
In the high-speed binary format (F5), the command interpreter is disabled. The Digital488 treats all bytes
received as data to be output to the Digital I/O ports. Each time it receives five bytes
it pulses the Data Strobe for approximately 15 microseconds. Using the Digital488 data is expected I
n a PORT5, PORT4, PORT3, PORT2, PORT1 sequence. Using the Digital488/32/OEM data is expected
in a PORT4, PORT3, PORT2, PORT1 sequence.
If only two bytes are received, with EOI asserted on the second byte, the Digital488 will update PORT5
with the first byte received PORT4 with the second and pulse the Data Strobe.
If using Digital488/32/OEM will update PORT4 with the first byte received, and PORT3 with the second
and pulse the Data Strobe. Since the interface treats all received characters as data, the Status (Un)
command will not be recognized.
Device Clear (DCL and SDC)
In the F0 thru F4 formats, Device Clear resets the Digital488 to power on defaults and pulses the Clear
output line for approximately 50 microseconds.
In the high-speed binary format (F5), it enables the command interpreter and ch anges the format to F0. All
other parameters remain unchanged. In addition, the Clear output line is not pulsed by DCL or SDC when
the interface is in F5. This is the only programmable method to exit the F5 format.
Group Execute Trigger (GET)
When the Digital488 recognizes a GET, it pulses the Trigger output line for approximately 50
microseconds.
or detects EOI
Interface Clear (IFC)
IFC places the Digital488 in the Talker/Listener Idle State and pulses the Clear output line for
approximately 50 microseconds.
Serial Poll Enable (SPE)
When Serial Poll Enabled, the Digital488 sets itself to respond to a serial poll with its serial poll status byte
if addressed to talk. When the serial poll byte is accepted by the controller, any pending SRQs are cleared.
The Digital488 will continue to try to output its serial poll response until it is serial poll disabled by the
controller.
Serial Poll Disable (SPD)
Disables the Digital488 from responding to serial polls by the controller.
Unlisten (UNL)
UNL places the Digital488 in the Listener Idle State.
Untalk (UNT)
UNT places the Digital488 in the Talker Idle State.
2-8, Getting Started 11-19-01 Digital488 User’s Manual
Installation
To begin operating the Digital488, plug the external power supply into the rear jack on the interface.
CAUTION
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.
WARNING
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.
After installing the power supply connector into the interface, turn on the Digital488 by depressing the rear
panel power switch. All the front panel LEDs should light for approximately on e second while the
Digital488 performs an internal ROM and RAM self check. At the end of this self-check, all indicators
should turn off except POWER.
If you obtain the above response then your Digital488 is aliv e and well. If all 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 to determine that the error is repeatable.
If the LEDs do not flash and the POWER indicator does not remain lit, there 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
Service Information section of this manual.
Digital488 User’s Manual 11-19-01 Getting Started, 2-9
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