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488
User Manual
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Black Box 488 User Manual

Order toll-free in the U.S.: Call 877-877-BBOX (outside U.S. call 724-746-5500) FREE technical support 24 hours a day, 7 days a week: Call 724-746-5500 or fax 724-746-0746 Mailing address: Black Box Corporation, 1000 Park Drive, Lawrence, PA 15055-1018 Web site: www.blackbox.com • E-mail: info@blackbox.com
CUSTOMER
SUPPORT
INFORMATION
MARCH 1997
IC027AE-R2
488 Controller
TALK
LISTEN
SRQ
ERROR
POWER
488 CONTROLLER
3
EUROPEAN UNION DECLARATION OF CONFORMITY
To maintain safety, emission, and immunity standards of this declaration, the following conditions must be met.
• Serial and IEEE cables must have a braided shield connected circumferentially to their connectors’ metal shells.
• All cable screw locks must be tightened at both ends of the cable.
• The host computer must be properly grounded.
• Some inaccuracy is to be expected when I/O leads are exposed to RF fields or transients.
• The operator must observe all safety cautions and operating conditions specified in the documentation for all hardware used.
• The host computer, peripheral equipment, power sources, and expansion hardware must be CE compliant.
• All power must be off to the device and externally connected equipment before internal access to the device is permitted.
• An external power supply is provided with this product. Its input is 105 to 125 VAC or 210 to 250 VAC, 50-60 Hz, 10 VA maximum power draw. Its 9-VDC output connects to the power input of the unit (marked 10VDC MAX @ 500 mA).
• The RS-232/422 terminal is meant to be connected only to devices with serial-communications-level signals. The IEEE 488 terminal is meant to be used only with non-isolated IEEE 488 systems. The common mode voltage (cable shell to earth) must be zero.
• Terminal Installation Category for CE Compliance is Category 1.
• Operating environment for CE compliance is: Indoor use at altitudes below 2000 m, 0 to 40°C, 80% maximum RH up to 31°C decreasing linearly 4%RH/°C to 40°C.
• Regarding DC power input: Please note that the power input is marked 10VDC MAX @ 600 mA. This is just something to check; check your equipment’s power input labels for “600 mA” (or even 500 mA).
WARNING!
Noted conditions pertain to potential safety hazards. When you see the WARNING!, IMPORTANT!, or CAUTION! notes, carefully read the information and be alert to the possibility of personal injury.
Failure to follow these directives voids emissions and immunity compliance.
488 CONTROLLER
4
Chapter Page
1. Specifications.....................................................................................................................................................8
2. Introduction ....................................................................................................................................................10
2.1 Description ...............................................................................................................................................10
2.2 Abbreviations............................................................................................................................................11
3. Getting Started ................................................................................................................................................12
3.1 Inspection .................................................................................................................................................12
3.2 Configuration ...........................................................................................................................................12
3.3 Serial-Port Settings ...................................................................................................................................14
3.3.1 Serial Baud Rate............................................................................................................................14
3.3.2 Serial Word Length (Data Bits)....................................................................................................15
3.3.3 Serial Stop Bits ..............................................................................................................................16
3.3.4 Serial Parity....................................................................................................................................16
3.3.5 Serial Echo.....................................................................................................................................17
3.3.6 Serial Handshake ..........................................................................................................................17
3.4 Selecting Terminator Substitution ..........................................................................................................18
3.4.1 Serial Terminator ..........................................................................................................................18
3.4.2 IEEE Bus Terminator....................................................................................................................19
3.5 Selecting the Mode ..................................................................................................................................19
3.6 Selecting the IEEE Address .....................................................................................................................20
3.7 Feature Selections ....................................................................................................................................21
3.7.1 Controller Pass-Thru Features .....................................................................................................21
3.7.2 Peripheral Pass-Thru Features .....................................................................................................22
3.8 Serial Interface .........................................................................................................................................22
3.8.1 RS-232/RS-422 Signal Level Selection.........................................................................................22
3.8.2 Serial Signal Descriptions.............................................................................................................23
3.8.3 Serial-Cable Wiring Diagrams ......................................................................................................24
3.9 General Operation ...................................................................................................................................26
3.10 Is Anyone Out There?............................................................................................................................27
4. IEEE Operating Modes ...................................................................................................................................28
4.1 Introduction .............................................................................................................................................28
4.2 Operating Mode Transitions ...................................................................................................................28
4.3 System Controller Mode ..........................................................................................................................30
4.4 System Controller, Not Active Controller Mode ....................................................................................31
4.5 Not System Controller Mode...................................................................................................................33
4.6 Active Controller, Not System Controller Mode ....................................................................................34
4.7 Controller Pass-Thru Mode .....................................................................................................................34
4.8 Peripheral Pass-Thru Mode .....................................................................................................................34
Contents
CONTENTS
5
Chapter Page
5. Command Descriptions ..................................................................................................................................35
5.1 Introduction .............................................................................................................................................35
5.2 Command-Description Format................................................................................................................36
5.2.1 Syntax.............................................................................................................................................36
5.2.2 Response........................................................................................................................................38
5.2.3 Mode..............................................................................................................................................38
5.2.4 Bus States.......................................................................................................................................39
5.3 Memory Use..............................................................................................................................................40
5.4 The Commands ........................................................................................................................................40
@ .............................................................................................................................................40
@@ ..........................................................................................................................................41
ABORT ...................................................................................................................................41
ARM ........................................................................................................................................42
CLEAR ....................................................................................................................................45
COUNT ..................................................................................................................................45
COMMENT ............................................................................................................................46
DELAY ....................................................................................................................................47
DISARM..................................................................................................................................47
DOMACRO ............................................................................................................................48
ENTER (Controller mode) ...................................................................................................48
ENTER (Peripheral mode) ...................................................................................................49
ERASE.....................................................................................................................................51
ERROR ...................................................................................................................................51
HELLO ...................................................................................................................................51
ID ............................................................................................................................................52
LOCAL ...................................................................................................................................53
LOCAL LOCKOUT or LOL .................................................................................................53
MACROENDM.......................................................................................................................54
MASK ......................................................................................................................................55
MEMORY................................................................................................................................56
ON <event> DOMACRO .......................................................................................................56
OUTPUT (Controller mode) ...............................................................................................59
OUTPUT (Peripheral mode) ...............................................................................................60
PASS CONTROL....................................................................................................................60
PPOLL ....................................................................................................................................61
PPOLL CONFIG or PPC .......................................................................................................62
PPOLL DISABLE or PPD ......................................................................................................62
PPOLL UNCONFIG or PPU .................................................................................................63
READ ......................................................................................................................................63
REMOTE ................................................................................................................................64
REQUEST...............................................................................................................................64
RESET.....................................................................................................................................65
RESUME.................................................................................................................................66
SEND ......................................................................................................................................66
SPOLL ....................................................................................................................................68
STATUS ..................................................................................................................................69
STERM....................................................................................................................................71
TERM......................................................................................................................................71
TIME OUT .............................................................................................................................72
TRACE....................................................................................................................................73
TRIGGER ...............................................................................................................................73
488 CONTROLLER
6
Chapter Page
6. Controller Pass-Thru Operation.....................................................................................................................74
6.1 Introduction .............................................................................................................................................74
6.2 Serial and IEEE Terminator Substitution ...............................................................................................74
6.3 IEEE Address Selection............................................................................................................................75
6.4 Talk Back on Terminator .........................................................................................................................75
6.5 Plotter Applications..................................................................................................................................76
6.6 Printer Applications .................................................................................................................................78
7. Peripheral Pass-Thru Operation ....................................................................................................................79
7.1 Introduction .............................................................................................................................................79
7.2 Serial and IEEE Input Buffers .................................................................................................................79
7.3 IEEE Data Transfers .................................................................................................................................80
7.3.1 Blind Bus Data Transfers ..............................................................................................................80
7.3.2 Controlled Bus Data Transfers .....................................................................................................81
7.4 Serial Poll Status Byte Register ................................................................................................................82
7.5 Use of Serial and Bus Terminators..........................................................................................................83
7.6 IEEE 488 Bus Implementation................................................................................................................83
7.6.1 My Talk Address (MTA)................................................................................................................83
7.6.2 My Listen Address (MLA) ............................................................................................................83
7.6.3 Device Clear (DCL and SDC) ......................................................................................................84
7.6.4 Interface Clear (IFC) ....................................................................................................................84
7.6.5 Serial Poll Enable (SPE)...............................................................................................................84
7.6.6 Serial Poll Disable (SPD)..............................................................................................................84
7.6.7 Unlisten (UNL).............................................................................................................................84
7.6.8 Untalk (UNT) ...............................................................................................................................84
7.7 IEEE Address Selection............................................................................................................................84
7.7.1 Listen Only Mode .........................................................................................................................84
8. IEEE 488 Primer..............................................................................................................................................85
8.1 History.......................................................................................................................................................85
8.2 General Structure.....................................................................................................................................85
8.3 Send It To My Address .............................................................................................................................87
8.4 Bus Management Lines............................................................................................................................87
8.4.1 Attention (ATN) ...........................................................................................................................87
8.4.2 Interface Clear (IFC) ....................................................................................................................87
8.4.3 Remote Enable (REN)..................................................................................................................87
8.4.4 End or Identify (EOI)...................................................................................................................87
8.4.5 Service Request (SRQ) .................................................................................................................87
8.5 Handshake Lines......................................................................................................................................88
8.5.1 Data Valid (DAV) ..........................................................................................................................88
8.5.2 Not Ready For Data (NRFD)........................................................................................................88
8.5.3 Not Data Accepted (NDAC).........................................................................................................88
8.6 Data Lines .................................................................................................................................................89
CONTENTS
7
Chapter Page
8.7 Multiline Commands ...............................................................................................................................89
8.7.1 Go To Local (GTL).......................................................................................................................89
8.7.2 Listen Address Group (LAG).......................................................................................................89
8.7.3 Unlisten (UNL).............................................................................................................................89
8.7.4 Talk Address Group (TAG) ..........................................................................................................89
8.7.5 Untalk (UNT) ...............................................................................................................................89
8.7.6 Local Lockout (LLO) ...................................................................................................................89
8.7.7 Device Clear (DCL) ......................................................................................................................89
8.7.8 Selected Device Clear (SDC)........................................................................................................89
8.7.9 Serial Poll Disable (SPD)..............................................................................................................89
8.7.10 Serial Poll Enable (SPE).............................................................................................................89
8.7.11 Group Execute Trigger (GET)...................................................................................................89
8.7.12 Take Control (TCT)....................................................................................................................89
8.7.13 Secondary Command Group (SCG)..........................................................................................90
8.7.14 Parallel Poll Configure (PPC)....................................................................................................90
8.7.15 Parallel Poll Unconfigure (PPU) ...............................................................................................90
8.8 More On Service Requests.......................................................................................................................90
8.8.1 Serial Poll.......................................................................................................................................90
8.8.2 Parallel Poll....................................................................................................................................90
9. Theory of Operation & Board Layout ...........................................................................................................91
9.1 Theory of Operation ................................................................................................................................91
9.2 Board Layout ............................................................................................................................................92
Appendix A: 488 Controller Command Summary............................................................................................94
Appendix B: 488 Controller Error Messages .....................................................................................................97
Appendix C: Character Codes and IEEE Multiline Messages ..........................................................................99
Appendix D: Sample Programs ........................................................................................................................101
Index ...................................................................................................................................................................103
TRADEMARKS USED IN THIS MANUAL
Macintosh
®
is a registered trademark of Apple Computer, Inc.
Hewlett-Packard
®
and HP®are registered trademarks of Hewlett-Packard.
AT
®
and IBM®are registered trademarks of IBM Corporation.
All applied-for and registered trademarks are the property of their respective owners.
488 CONTROLLER
8
488 Controller
IEEE 488-1978 Implementation — C1, C2, C3, C4, and C28 controller subsets. SH1, AH1, T6,
TE0, L4, LE0, SR1, RL0, PP0, DC1, DT1, E1.
Terminators — Selectable CR, LF, LF-CR, and CR-LF with EOI.
Connector — Standard IEEE 488 connector with metric studs.
Serial Interface
EIA RS-232C — AB, BA, BB, CA, CB
EIA RS-422A — Balanced voltage on TxD and RxD.
Character Set — Asynchronous bit serial.
Output Voltage — ±5 volts min (RS-232C); 3.5 volts typical (RS-422A)
Input Voltage — ±3 volts min.; ±15v max.
Baud Rate — Selectable 110, 300, 600, 1200, 1800, 2400, 3600, 4800, 7200,
9600, 19,200 and 57,600.
Data Format — Selectable 7 or 8 data bits; 1 or 2 stop bits; odd, even, mark,
space and no parity on transmit.
Duplex — Full with Echo/No Echo.
Serial Control — Selectable CTS/RTS or XON/XOFF.
Terminators — Selectable CR, LF, LF-CR, and CR-LF.
Connector — 25-pin Sub-D male. RS-232C DCE configured.
1. Specifications
CHAPTER 1: Specifications
9
General
Data Buffer — 32,000 characters total, dynamically allocated.
Indicators — LEDs for Talk, Listen, SRQ, Error and Power
Power — 105-125V or 210-250V; 50-60 Hz, 10 VA Max.
Size — 2.7"H x 5.5"W x 7.4"D (6.9 x 14 x 18.8 cm)
Weight — 3.6 lb. (1.6 kg)
Environment — 0 to 50 degrees Centigrade; 0 to 70% R.H. to 35 degrees
Centigrade. Linearly derate 3% R.H./degrees Centigrade from 35 to 50 degrees Centigrade.
Controls — Power Switch (external), IEEE and Serial parameter switches
(internal). Jumper selection of RS-232 or RS-422 operation (internal).
Certification — FCC, CE
WARNING!
Do not use this interface outdoors. The interface is intended for indoor use only. Using this equipment outdoors could result in equipment failure, bodily injury, or death.
CAUTION
Do not connect AC line power directly to the 488 Controller. Direct AC connection will damage equipment.
488 CONTROLLER
10
2.1 Description
The 488 Controller converts a host RS-232 or RS-422 computer into an IEEE 488 bus talker, listener and controller. The 488 Controller provides full IEEE 488-1978 bus implementation including advance capabilities such as PASS CONTROL, RECEIVE CONTROL, PARALLEL POLL, SERIAL POLL and SECONDARY ADDRESSING. The device may be located several hundred feet from the host and may control as many as fourteen 488 bus instruments. In the noncontroller mode the 488 Controller converts the host into a bus peripheral for data processing and mass storage.
The 488 Controller interprets simple high-level commands sent from the computer’s serial port and performs the necessary, and usually complex, bus control and handshaking. The commands and protocol are similar to those used by the Hewlett-Packard
®
HP-85 computer.
Additional features provide a transparent IEEE to serial converter and a serial to IEEE pass-thru controller.
As a serial-to-IEEE-488 converter, the 488 Controller receives data from a serial host, then automatically performs the bus sequences necessary to send this data to the IEEE 488 device. If desired, data can be requested from the IEEE 488 device and returned to the host.
As an IEEE-488-to-serial converter, the 488 Controller is a peripheral to an IEEE 488 controller. Data received from the controller is sent to the serial device and data received from the serial device is buffered for transmission to the IEEE 488 controller. The 488 Controller can inform the host, by the serial poll-status byte, that it has received data from the serial device.
2. Introduction
CHAPTER 2: Introduction
11
2.2 Abbreviations
The following IEEE 488 abbreviations are used throughout this manual.
addr n IEEE bus address “n”
ATN Attention line
CA Controller Active
CO Controller
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
PE Peripheral
PPC Parallel Poll Configure
PPU Parallel Poll Unconfigure
REN Remote Enable
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
488 CONTROLLER
12
3.1 Inspection
The 488 Controller was carefully inspected, both mechanically and electrically, prior to shipment. When you receive it carefully unpack all items from the shipping carton and check for any obvious signs of damage that may have occurred during shipment. Immediately report any damage found to the shipping agent. Remember to retain all shipping materials in the event that shipment back to the factory becomes necessary.
Every 488 Controller is shipped with the following:
• 488 Controller
• This instruction manual
• Power supply
3.2 Configuration
Three DIP switches internal to the 488 Controller set the configuration of the interface.
NOTE
Selectable functions are read only at power-on and should only be set prior to applying power to the interface.
The following figures illustrate the factory default conditions, which are:
Serial Por
t: IEEE:
9600 Baud Mode = System Controller
8 Data Bits Address = 10
2 Stop Bits Bus Terminator = CR-LF; EOI Disabled
No Parity Talk-back Enabled
Serial Terminator = CR-LF
Echo Disabled
RTS/CTS Handshake
3. Getting Started
CHAPTER 3: Getting Started
13
Figure 3-1. SW3 Factory-Default Settings.
Figure 3-2. SW2 Factory-Default Settings.
Figure 3-3. SW1 Factory-Default Settings.
1 2 3 4 5 6 7 8
OPEN
SW1
Baud Rate
Handshake
Word Length
9600 RTS/CTS 8 Data Bits
Switch
Side
View
DOT
Pass-Thru Feature
Enabled
Stop Bits
2 Stop Bits
1 2 3 4 5 6 7 8
OPEN
SW2
Mode
Serial Term
Echo
SC CR-LF
Switch
Side
View
DOT
Parity
No Echo No Parity
1 2 3 4 5
6
7 8
OPEN
SW3
IEEE Addr IEEE Term
EOI
10 CR-LF Disabled
Switch
Side
View
DOT
488 CONTROLLER
14
Note that the 488 Controller comes configured as an IEEE controller. In this mode the 488 Controller is designed to allow an RS-232 host computer to control up to 14 IEEE 488 devices. This mode of operation is described in detail, along with its command descriptions, in Chapters 4 and 5. These sections also cover the peripheral mode of operation.
The 488 Controller can be configured to transparently communicate with a single IEEE peripheral, such as a plotter. This Controller Pass-Thru mode is described in detail in Chapter 6.
The 488 Controller may also be configured as a transparent IEEE Pass-Thru Peripheral. As a Pass-Thru Peripheral, it allows an IEEE controller to communicate with an RS-232 device. The Peripheral Pass-Thru mode of operation is described in detail in Chapter 7.
To modify any of these defaults, follow this simple procedure:
1) Disconnect the power supply from the AC line and from the 488 Controller. Also disconnect any IEEE or serial cables prior to disassembly.
WARNING
Never open the 488 Controller’s case while it is connected to the AC line. Failure to observe this warning may result in equipment failure, personal injury or death.
2) Place the 488 Controller upside down on a flat surface. Remove the four screws located near the rubber feet.
3) Return the interface to the upright position and carefully remove the top cover.
4) Change whichever DIP-switch settings you need to change.
5) When you have made all of your changes, reverse this procedure to reassemble the 488 Controller.
3.3 Serial-Port Settings
The first parameters to configure are those that correspond to the RS-232 port. These include baud rate, word length, number of stop bits, parity selection and type of RS-232 handshake. Each of these is described in the following sections.
3.3.1 S
ERIAL BAUD RATE
The “baud rate” is the number of serial bits per second transferred into and out of the serial interface. SW1­1 through SW1-4 determine the serial baud rate. The factory-default baud rate is 9600 baud. Baud rates may be selected from 110 to 57,600 baud. Refer to the following diagram for specific baud rates.
CHAPTER 3: Getting Started
15
Figure 3-4. Switch SW1: Selecting the Serial Baud Rate.
3.3.2 SERIAL WORD LENGTH (DATA BITS)
SW1-6 determines the number of data bits, often referred to as word length, for each serial character transmitted or received. The factory default is 8 data bits.
Figure 3-5. Switch SW1: Selecting the Serial Word Length (Data Bits).
1 2 3 4 5
6
7 8
OPEN
8 Data Bits
1 2 3 4 5
6
7 8
OPEN
7 Data Bits
Switch
Side
View
DOT
Switch
Side View
DOT
110
1 2 3 4 567 8
OPEN
1 2 3 4 567 8
OPEN
1800
300
1 2 3 4 567 8
OPEN
110
1 2 3 4 567 8
OPEN
1 2 3 4 567 8
OPEN
2400
110
1 2 3 4 567 8
OPEN
1 2 3 4 567 8
OPEN
3600
1 2 3 4 567 8
OPEN
4800135
1 2 3 4 567 8
OPEN
1 2 3 4 567 8
OPEN
720015 0
1 2 3 4 567 8
OPEN
1 2 3 4 567 8
OPEN
9600
600
1 2 3 4 567 8
OPEN
1 2 3 4 567 8
OPEN
19,200
1200
1 2 3 4 567 8
OPEN
1 2 3 4 567 8
OPEN
57,600
488 CONTROLLER
16
3.3.3 SERIAL STOP BITS
Switch SW1-8 determines the number of stop bits contained in each serial character transmitted and received. The factory default is 2 stop bits.
Figure 3-6. Switch SW1: Selecting the Serial Stop Bits.
3.3.4 S
ERIAL PARITY
Serial Parity is selected with S2-6 through S2-8. The 488 Controller generates the selected parity during serial transmissions but it does not check parity on data that is received. The factory default is parity disabled.
Figure 3-7. Switch SW2: Selecting the Serial Parity.
Switch
Side View
DOT
1 2 3 4 567 8
OPEN
Mark Parity
1 2 3 4 567 8
OPEN
Odd Parity
1 2 3 4 567 8
OPEN
Space Parity
1 2 3 4 567 8
OPEN
Even Parity
1 2 3 4 567 8
OPEN
Parity Disabled
Switch
Side
View
DOT
1 2 3 4 5
6
7 8
OPEN
2 Stop Bits
1 2 3 4 5
6
7 8
OPEN
1 Stop Bit
CHAPTER 3: Getting Started
17
3.3.5 SERIAL ECHO
Serial data sent to the 488 Controller will be echoed back to the serial host if SW2-5 is set to the open position. The factory default is Echo Disabled.
Figure 3-8. Switch SW2: Enabling or Disabling Echo.
3.3.6 S
ERIAL HANDSHAKE
Switch SW1-5 is used to select hardware [RTS/CTS] or software [X-ON/X-OFF] serial handshake control.
With X-ON/X-OFF, the 488 Controller issues an X-OFF character [ASCII value of &H13] when its buffer memory is near full. When the X-OFF character is sent, there are still more than 1000 character locations remaining to protect against buffer overrun. When it is able to accept more information, the 488 Controller issues an X-ON character [ASCII value of &H11]. The 488 Controller also accepts X-ON/ X-OFF on transmit from the serial host it is communicating with. RTS/CTS serial control becomes inactive when X-ON/X-OFF is enabled. The RTS output is, however, set to an active high state. The CTS input is not used for this handshake and may be left floating (unconnected).
With RTS/CTS, the 488 Controller un-asserts RTS (sets RTS low) when its buffer memory is near full. When RTS is un-asserted, there are still more than 1000 character locations remaining to protect against buffer overrun. When it is able to accept more information, the 488 Controller asserts RTS (sets RTS high). The 488 Controller will not transmit data to the serial host if it detects the CTS input un-asserted (low) when configured for this hardware handshake.
The factory-default serial control is hardware, RTS/CTS.
Figure 3-9. Switch SW1: Selecting the Serial Handshake.
Switch
Side
View
DOT
1 2 3 4 5
6
7 8
OPEN
RTS/CTS
1 2 3 4 5
6
7 8
OPEN
X-ON/X-OFF
1 2 3 4 5
6
7 8
OPEN
Echo Disabled
1 2 3 4 5
6
7 8
OPEN
Echo Enabled
Switch
Side
View
DOT
488 CONTROLLER
18
3.4 Selecting Terminator Substitution
In the Controller and Peripheral Modes, the 488 Controller is not sensitive as to whether CR or LF is used as a serial input terminator to a command. In general, it requires only one of either to cause command execution. The IEEE input terminator is fixed to LF. The switches that allow terminator selection, shown in the following diagrams, set only the serial output and IEEE output terminators for these modes of operation.
In the transparent Pass-Thru modes, the 488 Controller can be configured to provide RS-232-to-IEEE 488 and IEEE-488-to-RS-232 terminator substitution. This is useful when interfacing an RS-232 device which only issues carriage return [CR] as an output terminator to an IEEE controller which expects a carriage return followed by a line feed [CR-LF].
In the above case, the serial terminator should be selected for CR Only while the IEEE terminator is set to CR-LF. When a serial CR character is received, it is discarded, and an IEEE CR-LF is substituted for it. In the IEEE-to-RS-232 direction, the IEEE CR is unconditionally discarded. Upon receipt of the IEEE LF, a serial CR is substituted.
The 488 Controller can be made totally data transparent in the Pass-Thru modes by setting both the serial and IEEE terminators to be CR Only or LF Only.
3.4.1 S
ERIAL TERMINATOR
SW2-3 and SW2-4 select the serial terminators for the serial input (Pass-Thru Modes Only) and output. The factory default is CR-LF.
Figure 3-10. Switch SW2: Selecting the Serial Terminator.
Switch
Side
View
DOT
CR Only
1 2 3 4 5
6
7 8
OPEN
LF-CR
1 2 3 4 5
6
7 8
OPEN
1 2 3 4 5
6
7 8
OPEN
LF Only
1 2 3 4 5
6
7 8
OPEN
CR-LF
CHAPTER 3: Getting Started
19
3.4.2 IEEE BUS TERMINATOR
SW3-6 through SW3-8 set the IEEE bus terminators used for data sent or received (Pass-Thru modes only) by the 488 Controller. EOI, a line used to signal the end of a multiple character bus transfer, may also be enabled. If enabled, EOI is asserted when the last selected bus terminator is sent. Factory default is CR-LF with EOI disabled.
Figure 3-11. Switch SW3: Selecting the IEEE Bus Terminator.
3.5 Selecting the Mode
SW2-1 and SW2-2 set the major operating mode of the 488 Controller. There are four distinct modes of operation.
1. System Controller
2. Peripheral
3. Controller Pass-Thru
4. Peripheral Pass-Thru
Switch
Side
View
DOT
1 2 3 4 5
6
7 8
OPEN
LF Only
1 2 3 4 5
6
7 8
OPEN
CR-LF
1 2 3 4 5
6
7 8
OPEN
CR Only
1 2 3 4 5
6
7 8
OPEN
LF-CR
1 2 3 4 5
6
7 8
OPEN
EOI Disabled
1 2 3 4 5
6
7 8
OPEN
EOI Enabled
488 CONTROLLER
20
As a System Controller, the 488 Controller accepts simple high-level ASCII commands from a serial host. It interprets these commands and performs the required bus action to bi-directionally communicate with up to 14 IEEE devices. As a Peripheral, the 488 Controller becomes a bus device. It accepts simple high-level ASCII commands from a serial host and interprets these commands and status to communicate with another IEEE controller. Applications include computer controlled automatic test systems. These modes of operation are discussed in Chapters 4 and 5.
The IEEE Controller Pass-Thru (RS-232 to IEEE Converter) mode allows a serial host device to send data to a single IEEE bus peripheral. Applications include interfacing a listen-only or addressable IEEE printer/plotter to a serial printer port. Refer to Chapter 6 for more detailed information on the Controller Pass-Thru mode of operation.
The Peripheral Pass-Thru mode is used when interfacing a serial device to an IEEE controller. Data which is sent by the IEEE controller to the 488 Controller is transmitted out its serial port. Data received from the serial device is buffered by the 488 Controller until read by the IEEE controller. Refer to Chapter 7 for more detailed information on the Peripheral Pass-Thru mode of operation.
The factory default is the System Controller mode.
Figure 3-12. Switch SW2: Selecting the Mode.
3.6 Selecting the IEEE Address
SW3-1 through SW3-5 select the IEEE bus address of the 488 Controller when in the System Controller, Peripheral and Peripheral Pass-Thru modes. These same switches are used in the Controller Pass-Thru mode to select the address of the device that will be controlled. (Refer to Chapter 7 for additional information.) The address is selected by simple binary weighting, with SW3-1 being the least significant bit and SW3-5 the most significant. The factory default is address 10.
Listen Only is a special type of Peripheral Pass-Thru operation. In the Listen Only mode the 488 Controller accepts all data transmitted on the bus, ignoring any bus addressing, and transfers it out its serial port. The 488 Controller is set to Listen Only mode by setting its address to 31. If the IEEE address is set to 31 in the System Controller, Peripheral, or Peripheral Pass-Thru mode, it is adjusted to address 30.
Switch
Side
View
DOT
1 2 3 4 5
6
7 8
OPEN
Controller Pass-Thru
1 2 3 4 5
6
7 8
OPEN
Peripheral Pass-Thru
1 2 3 4 5
6
7 8
OPEN
Peripheral
System Controller
1 2 3 4 5
6
7 8
OPEN
CHAPTER 3: Getting Started
21
Figure 3-13. Switch SW3: Selecting the IEEE Address.
3.7 Feature Selections
The functions of the remaining switches are dependent on the mode selected. A brief description of each of these features follows. You should refer to the listed sections for additional information.
3.7.1 CONTROLLER PASS-THRU FEATURES
In the IEEE Controller (RS-232-to-IEEE-488 converter) mode, SW1-7 is used to determine whether the interface should, after sending the IEEE bus terminators, address the attached bus device to talk. The factory default is Talk-back On Terminator enabled.
Refer to Chapter 6 for complete details on these features.
Figure 3-14. Switch SW1: Enabling or Disabling “Talk Back on Terminator” in Controller Mode.
Switch
Side View
DOT
1 2 3 4 5
6
7 8
OPEN
Talk-Back on
Terminator Disabled
1 2 3 4 5
6
7 8
OPEN
Talk-Back on
Terminator Enabled
Switch
Side
View
DOT
1 2 3 4 5
6
7 8
OPEN
0
1
0 x 16 1 x 8 0 x 4 1 x 2 0 x 1
=0 =8 =0 =2
+ -0
IEEE Address = 10
488 CONTROLLER
22
3.7.2 PERIPHERAL PASS-THRU FEATURES
In the Peripheral Pass-Thru (IEEE-488-to-RS-232 converter) mode, SW1-7 enables the interface to assert the SRQ IEEE bus interface line to indicate that it has received the last switch selected serial terminator character from the serial device.
Figure 3-15. Switch SW1: Enabling or Disabling SRQ on Last Serial Terminator in Peripheral Mode.
3.8 Serial Interface
The 488 Controller has the ability to output signal levels that are compatible with either RS-232 or RS-422. An internal DIP shorting plug determines which electrical specification is chosen. If the interface is to be connected to an IBM
®
PC or compatible, the RS-232 level should be selected. If it will be connected to a
Macintosh
®
, the RS-422 level should be used. For connection to other computers, refer to the
manufacturer’s manual to determine which levels are supported.
3.8.1 RS-232/RS-422 SIGNAL LEVEL SELECTION
The 488 Controller’s factory default signal levels are compatible with RS-232. To select RS-422 levels, carefully remove the 8-position shorting plug with a small flat blade screwdriver from J106. Install the DIP jumper into J205 making certain that all of the pins on the shorting plug are inserted correctly.
Figure 3-16. Selecting RS-232 or RS-422 Signal Levels.
Switch
Side View
DOT
1 2 3 4 5
6
7 8
OPEN
SRQ on Last
Terminator Disabled
1 2 3 4 5
6
7 8
OPEN
SRQ on Last
Terminator Enabled
Shorting Plug
RS-232
RS-422
CHAPTER 3: Getting Started
23
3.8.2 SERIAL SIGNAL DESCRIPTIONS
The 488 Controller is equipped with a standard DB25 female connector on its rear panel and requires a standard DB25 male mating connector. The 488 Controller’s connector is configured as DCE type equipment for RS-232 communications, which means the 488 Controller always transmits data on Pin 3 and receives data on Pin 2. The following lists and describes the RS-232 and RS-422 signals provided on the 488 Controller.
Figure 3-17. Rear View of the 488 Controller’s Serial Connector.
-RxD Receive Data—Input—Pin 2
This pin accepts serial data sent by the RS-232 or RS-422 host. The serial data is expected with the word length, baud rate, stop bits, and parity selected by the internal switches. The signal level is low true.
-TxD Transmit Data—Output—Pin 3
This pin transmits serial data to the RS-232 or RS-422 host. The serial data is sent with the word length, baud rate, stop bits, and parity selected by the internal switches. The signal level is low true.
CTS Clear To Send—Input—Pin 4
The CTS input is used as a hardware-handshake line to prevent the 488 Controller from transmitting serial data when the RS-232 host is not ready to accept it. When RTS/CTS handshake is selected on the internal switches, the 488 Controller will not transmit data out -TxD while this line is un-asserted (lowered). If the RS-232 host is not capable of driving this line it can be connected to the Vtest output (Pin 6) of the 488 Controller. If X-ON/X-OFF handshake is selected, the CTS line is not tested to determine if it can transmit data.
RTS Request To Send—Output—Pin 5
The RTS output is used as a hardware handshake line to prevent the RS-232/RS-422 host from transmitting serial data if the 488 Controller is not ready to accept it. When RTS/CTS handshake is selected on the internal switches, the 488 Controller will drive the RTS output high when there are more than 1000 character locations available in its internal buffer. If the number of available locations drops to less than 1000, the 488 Controller will un-assert (lower) this output. If X-ON/X-OFF handshake is selected, the RTS line will be permanently driven active high.
13 1
25 14
-RXD
-TXD
CTS
RTS
+VTEST
GND
+VTEST
+RXD
+TXD
488 CONTROLLER
24
Vtest Test Voltage—Output—Pin 6
This pin is connected to +5 volts through a 1K resistor. It is also common to Vtest on pin 9.
Gnd Ground—Pin 7
This pin sets the ground reference point for the other RS-232 inputs and outputs.
Vtest Test Voltage—Output—Pin 9
This pin is connected to 5 volts through a 1K resistor. It is also common to Vtest on pin 6.
+RxD Receive Data Plus—Input—Pin 14
This pin accepts serial data sent by the RS-422 host. The serial data is expected with the word length, baud rate, stop bits, and parity selected by the internal switches. The signal level is high true and only connected to this pin when RS-422 operation is selected. It is 180 degrees out of phase with -RxD.
+TxD Transmit Data Plus—Output—Pin 16
This pin transmits serial data to the RS-422 host. The serial data is sent with the word length, baud rate, stop bits, and parity selected by the internal switches. The signal level is high true and only connected to this pin when RS-422 operation is selected. It is 180 degrees out of phase with -TxD.
3.8.3 S
ERIAL-CABLE WIRING DIAGRAMS
If a cable was not purchased with the 488 Controller, the following diagrams will be helpful in making your own cable. Simple soldering skills and an attention to detail will ensure successful construction.
Figure 3-18. Wiring Diagram: Macintosh to 488 Controller.
Mini DIN8 Male DB25 Male
RTS 1 CTS 2
-TxD 3 Gnd 4
-RxD 5
+TxD 6
+RxD 8
4 CTS 5 RTS 2 -RxD 7 Gnd 3 -TxD 14 +RxD 16 +TxD
CHAPTER 3: Getting Started
25
Figure 3-19. Wiring Diagram: IBM PC or Compatible with DB25
Serial Connector to 488 Controller (RS-232).
Figure 3-20. Wiring Diagram: IBM AT
®
or Compatible with DB9
Serial Connector to 488 Controller (RS-232).
NOTE
Standard AT 9-pin-to-25-pin adapter cables are not wired as shown above and will not work with the 488 Controller.
DCD 1
-RxD 2 3 -TxD
-TxD 3 2 -RxD DTR 4
Gnd 5 7 Gnd
DSR 6
RTS 7 4 CTS
DB9 Female DB25 Male
CTS 8 5 RTS
-TxD 2 2 -RxD
-RxD 3 3 -TxD RTS 4 4 CTS CTS 5 5 RTS
DSR 6 6 V test
Gnd 7
7 Gnd
DB25 Female DB25 Male
488 CONTROLLER
26
3.9 General Operation
Refer to the following sections for specific operational modes. This section gives a general test of function­ality. After setting the power-on defaults and reassembling the 488 Controller, plug the power-supply connector into the rear jack on the interface.
CAUTION
Never plug the power supply into the 488 Controller while it is connected to AC line power. If you do, you could damage the 488 Controller.
WARNING
The power supply provided with the interface is intended for indoor use only. Using it outdoors could result in equipment failure, personal injury, or death.
After plugging the power supply connector into the 488 Controller, plug the power supply into AC line power. Turn the rear-panel power switch ON (the “1” position). All the front-panel indicators should light momentarily while the 488 Controller performs an internal ROM and RAM self-check. At the end of this self-check, all indicators except POWER should turn off.
If there is an error in the ROM checksum, all of the LEDs will remain on. Flashing LEDs indicate a RAM failure. Should such an error occur, turn the rear panel switch to the OFF [0] position and retry the above procedure.
If the front-panel indicators 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 the AC line and the rear-panel connection of the power supply.
If proper operation is obtained, connect an interface cable to the rear of the 488 Controller (25-Pin Sub-D). Connect the other end to the host’s serial port. Except for connecting IEEE bus instruments, the 488 Controller is installed and ready to use.
WARNING
The 488 Controller makes its earth ground connection through the serial interface cable. It should only be connected to IEEE bus devices after being first connected to the host. Failure to do so may allow the 488 Controller to float to a bus device test voltage. This could result in damage to the 488 Controller, personal injury, or death.
CHAPTER 3: Getting Started
27
3.10 Is Anyone Out There?
Before connecting any IEEE bus devices to the 488 Controller, try this simple operational check. The 488 Controller must be configured for either System Controller or Peripheral mode operation. This test will not work in either of the Pass-Thru modes.
Running BASIC on the host, or any programming language which supports the serial ports, type the following (or its equivalent).
OPEN "COM1:9600, N, 8, 2, cd, ds" AS 1 [Return]
PRINT #1,"HELLO" [Return]
LINE INPUT #1,A$ [Return]
PRINT A$ [Return]
The 488 Controller will respond with (and the host will display):
488 Controller Revision N.N Copyright (C) 1988
where N.N is the release and revision number of the firmware.
If you obtain the response above, then your 488 Controller is alive and well and ready to connect your host to the powerful IEEE-488 General Purpose Interface Bus. If you did not receive the message above, check for proper connection and fit of the interface cable. If, after reviewing the 488 Controller for proper installation, call your supplier.
488 CONTROLLER
28
4.1 Introduction
There are four types of IEEE bus devices: Active Controllers, Peripherals, Talk-Only devices, and Listen­Always devices. Talk-Only and Listen-Always devices are usually used together, in simple systems, such as a Talk-Only digitizer sending results to a Listen-Always plotter. In these simple systems, no controller is needed, because the talker assumes that it is the only talker on the bus, and the listener(s) assume that they are all supposed to receive all the data sent over the bus. This is a simple and effective method of transferring data from one device to another, but is not adequate for more complex systems where, for example, one computer is controlling many different bus devices.
In more complex systems, the Active Controller sends commands to the various bus Peripherals telling them what to do. Commands such as Unlisten, Listen Address Group, Untalk, and Talk Address Group are sent by the controller to specify which device is to send data, and which devices are to receive it. For more details about the IEEE bus protocols see Chapter 8.
When an IEEE bus system is first turned on, some device must be the Active Controller. This device is the System Controller and always keeps some control of the bus. In particular, the System Controller controls the Interface Clear (IFC) and Remote Enable (REN) bus management lines. By asserting Interface Clear, the System Controller forces all the other bus devices to stop their bus operations, and regains control as the Active Controller.
4.2 Operating Mode Transitions
The System Controller is initially the Active Controller. It can, if desired, pass control to another device and thereby make that device the Active Controller. Note that the System Controller remains the System Controller, even when it is not the Active Controller. Of course, the device to which control is passed must be capable of taking on the role of Active Controller. It would make no sense to try to pass control to a printer. Control should only be passed to other computers that are capable, and ready, to become the Active Controller. Further, note that there must be exactly one System Controller on the IEEE bus. All other potential controllers must be configured as Peripherals when they power up.
The state diagram on the next page shows the relationships between the various operating modes. The top half of the state diagram shows the two operating states of a System Controller. At power-on, it is the active controller. It directs the bus transfers by sending the bus commands mentioned previously. It also has control of the Interface Clear and Remote Enable bus lines. The System Controller can pulse Interface Clear to reset all of the other bus devices.
As shown in the diagram, the System Controller can pass control to some other bus device and thereby become a Peripheral to the new Active Controller. If the System Controller receives control from the new Active Controller, then it will once again become the Active Controller. The System Controller can also force the Active Controller to relinquish control by asserting the Interface Clear signal.
The bottom half of the state diagram shows the two operating states of a Not System Controller device. At power on, it is a Peripheral to the System Controller, which is the Active Controller. If it receives control from the Active Controller, it becomes the new Active Controller. Even though it is the Active Controller, it is still not the System Controller. The System Controller can force the Active Controller to give up control by asserting Interface Clear. The Active Controller can also give up control by passing control to another device, which may or may not be the System Controller.
4. IEEE Operating Modes
CHAPTER 4: IEEE Operating Modes
29
Figure 4-1. IEEE Bus Operating Modes State Diagram.
In summary, a bus device is set in hardware as either the sole System Controller in the system, or as a non­System Controller. At power on, the System Controller is the Active Controller, and the other devices are Peripherals. The System Controller can give up control by Passing Control, and can regain control by asserting Interface Clear, or by receiving control. A Peripheral can become the Active Controller by receiving control, and can give up control by Passing Control, or upon detecting Interface Clear.
Active
System
Controller
SC-CA
Active
Controller,
Not System
Controller
*SC-CA
System Controller, Not Active
SC-*CA
Peripheral,
Not System
Controller
*SC-*CA
Power On
Power On
Controller Active (CA) Peripheral (*CA)
Not System Controller (*SC)
Passes Control
Receives Control or
Asserts Interface Clear
Receives Control
Passes Control or
Detects Interface Clear
System Controller (SC)
488 CONTROLLER
30
4.3 System Controller Mode
The most common 488 Controller configuration is as the System Controller, controlling several IEEE-bus instruments. In this mode, the 488 Controller can perform all of the various IEEE-bus protocols necessary to control and communicate with any IEEE-488-bus devices. As the System Controller in the Active Controller mode, the 488 Controller can use all of the commands available for the Active Controller state, plus control the Interface Clear and Remote Enable lines. The allowed bus commands and their actions are as follows:
ABORT Pulse Interface Clear.
LOCAL Unassert Remote Enable, or send Go To Local to selected devices.
REMOTE Assert Remote Enable, optionally setting devices to Remote.
LOCAL LOCKOUT Prevent local (front-panel) control of bus devices.
CLEAR Clear all or selected devices. TRIGGER Trigger selected devices.
ENTER Receive data from a bus device. OUTPUT Send data to bus devices.
PASS CONTROL Give up control to another device which becomes the Active
Controller.
SPOLL Serial Poll a bus device, or check the Service Request state.
PPOLL Parallel Poll the bus. PPOLL CONFIG Configure Parallel Poll responses. PPOLL DISABLE Disable the Parallel Poll response of selected bus devices. PPOLL UNCONFIG Disable the Parallel Poll response of all bus devices.
SEND Send low-level bus sequences. RESUME Unassert Attention. Used to allow Peripheral-to-Peripheral transfers.
CHAPTER 4: IEEE Operating Modes
31
4.4 System Controller, Not Active Controller Mode
After Passing Control to another device, the System Controller is no longer the Active Controller. It acts as a Peripheral to the new Active Controller, and the allowed bus commands and their actions are modified accordingly. However, it still maintains control of the Interface Clear and Remote Enable lines. The available bus commands and their actions are:
ABORT Pulse Interface Clear.
LOCAL Unassert Remote Enable. REMOTE Assert Remote Enable.
ENTER Receive data from a bus device as directed by the Active Controller. OUTPUT Send data to bus devices as directed by the Active Controller.
REQUEST Set own Serial Poll request (including Service Request) status. SPOLL Get own Serial Poll request status.
As a bus Peripheral, the 488 Controller must respond to the commands issued by the Active Controller. The controller can, for example, address the 488 Controller to listen in preparation for sending data. There are two ways of detecting our being addressed to listen: through the STATUS command, or by detecting an event with the ARM or ON DOMACRO commands.
The STATUS 1 command can be used to watch for commands from the Active Controller. The Operating Mode, which is a “P” while the 488 Controller is a Peripheral, will change to a “C” if the Active Controller Passes Control to the 488 Controller. The Addressed State will go from Idle (“I”) to Listener (“L”) or Talker (“T”) if the 488 Controller is addressed to listen or to talk, and will go back to Idle (“I”) when the Active Controller issues Unlisten (UNL), Untalk (UNT), or specifies another talker (TAG). The Triggered (“T1”) and Cleared (“C1”) indicators will be set when the 488 Controller is triggered or cleared, and reset when STATUS 1 is read. The Address Change indicator will be set (“G1”) when the address state changes. These indicators allow the program to sense the commands issued to the 488 Controller by the Active Controller. The following BASIC program fragment illustrates the use of the Address Change and Addressed State indicators to communicate with the Active Controller:
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