Ni GPIB Reference User Manual
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GPIB
GPIB Reference Manual for
VXIpc
™
Embedded Controllers and VxWorks
GPIB for VXIpc Controllers and VxWorks
December 1997 Edition
Part Number 321858A-01
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© Copyright 1997 National Instruments Corporation. All rights reserved.
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Contents
About This Manual
Chapter 1
Introduction
Controller-In-Charge and System Controller ....................................................1-1
Handshake Lines .................................................................................1-3
Interface Management Lines...............................................................1-3
Chapter 2
Developing Your Application with the VxWorks Drivers
Repeat Addressing ..............................................................................2-7
Termination Method ...........................................................................2-7
© National Instruments Corporation v GPIB for VXIpc Controllers and VxWorks
Contents
Chapter 3
NI-488 Functions
Chapter 4
GPIB Programming Techniques
Service Requests from IEEE 488 Devices ........................................................ 4-3
Service Requests from IEEE 488.2 Devices ..................................................... 4-3
GPIB for VXIpc Controllers and VxWorks vi © National Instruments Corporation
Contents
SRQ and Serial Polling with NI-488 Functions ................................................4-3
Implementing a Parallel Poll with NI-488 Functions........................................4-4
Appendix A
Multiline Interface Messages
Appendix B
Status Word Conditions
Appendix C
Error Codes and Solutions
Appendix D
Customer Communication
© National Instruments Corporation vii GPIB for VXIpc Controllers and VxWorks
Contents
Glossary
Index
Figures
Linear and Star System Configuration.................................................... 1-4
Example of Multiboard System Setup .................................................... 1-5
Tables
GPIB Handshake Lines........................................................................... 1-3
GPIB Interface Management Lines ........................................................ 1-3
Multiline Interface Messages .................................................................. A-2
GPIB for VXIpc Controllers and VxWorks viii © National Instruments Corporation
About This Manual
This manual describes the features and functions of the GPIB driver software for VxWorks and VXIpc embedded controllers. This manual assumes that you are already familiar with operating system fundamentals and VxWorks device driver development concepts.
Organization of This Manual
This manual is organized as follows:
•
Chapter 1, Introduction , gives an overview of GPIB and describes how
to set up your VxWorks system.
•
Chapter 2, Developing Your Application with the VxWorks Drivers
, explains how to use the VxWorks GPIB drivers, and how to develop a GPIB application using the NI-488 API.
•
Chapter 3, NI-488 Functions , lists the NI-488 functions and describes
the purpose, format, input and output parameters, and possible errors for each function.
•
Chapter 4, GPIB Programming Techniques , describes techniques for
using some NI-488 functions in your application.
•
Appendix A, Multiline Interface Messages , contains a multiline
interface message reference list, which describes the mnemonics and messages that correspond to the interface functions.
•
Appendix B, Status Word Conditions , describes the conditions
reported in the status word, ibsta .
•
Appendix C, Error Codes and Solutions , describes each error,
including conditions under which it might occur and possible solutions.
•
Appendix D, Customer Communication , contains forms you can use to
request help from National Instruments or to comment on our products and manuals.
•
contains an alphabetical list and description of terms used in this manual, including abbreviations, acronyms, metric prefixes, mnemonics, and symbols.
•
contains an alphabetical list of key terms and topics in this manual, including the page where you can find each one.
© National Instruments Corporation ix GPIB for VXIpc Controllers and VxWorks
About This Manual
Conventions Used in This Manual
bold italic
IEEE 488 and
IEEE 488.2
italic monospace monospace bold monospace italic paths
The following conventions are used in this manual.
This icon to the left of bold italicized text denotes a note, which alerts you to important information.
Bold italic text denotes a note, caution, or warning.
IEEE 488 and IEEE 488.2 refer to the ANSI/IEEE Standard 488.1-1987 and the ANSI/IEEE Standard 488.2-1992, respectively, which define the
GPIB.
Italic text denotes emphasis, a cross reference, or an introduction to a key concept. This font also denotes text for which you supply the appropriate word or value.
Text in this font denotes text or characters that you should literally enter from the keyboard, sections of code, programming examples, and syntax examples. This font is also used for the proper names of disk drives, paths, directories, programs, subprograms, subroutines, device names, functions, operations, variables, filenames and extensions, and for statements and comments taken from programs.
Bold text in this font denotes the messages and responses that the computer automatically prints to the screen. This font also emphasizes lines of code that are different from the other examples.
Italic text in this font denotes that you must enter the appropriate words or values in the place of these items.
Paths in this manual are denoted using backslashes (\) or forward slashes (/) to separate drive names, directories, folders, and files.
Related Documentation
The following documents contain information that you may find helpful as you read this manual:
• ANSI/IEEE Standard 488.1-1987, IEEE Standard Digital Interface for Programmable Instrumentation
• ANSI/IEEE Standard 488.2-1992, IEEE Standard Codes, Formats,
Protocols, and Common Commands
GPIB for VXIpc Controllers and VxWorks x © National Instruments Corporation
About This Manual
Customer Communication
National Instruments wants to receive your comments on our products and manuals. We are interested in the applications you develop with our products, and we want to help if you have problems with them. To make it easy for you to contact us, this manual contains comment and configuration
forms for you to complete. These forms are in Appendix D, Customer
Communication , at the end of this manual.
© National Instruments Corporation xi GPIB for VXIpc Controllers and VxWorks
1
Introduction
This chapter gives an overview of GPIB and describes how to set up your
VxWorks system.
GPIB Overview
The ANSI/IEEE Standard 488.1-1987, also known as GPIB (General
Purpose Interface Bus), describes a standard interface for communication between instruments and controllers from various vendors. It contains information about electrical, mechanical, and functional specifications.
The GPIB is a digital, 8-bit parallel communications interface with data transfer rates of 1 Mbyte/s and above, using a 3-wire handshake. The bus supports one System Controller, usually a computer, and up to
14 additional instruments. The ANSI/IEEE Standard 488.2-1992 extends
IEEE 488.1 by defining a bus communication protocol, a common set of data codes and formats, and a generic set of common device commands.
Talkers, Listeners, and Controllers
GPIB devices can be Talkers, Listeners, or Controllers. A Talker sends out data messages. Listeners receive data messages. The Controller, usually a computer, manages the flow of information on the bus. It defines the communication links and sends GPIB commands to devices.
Some devices are capable of playing more than one role. A digital voltmeter, for example, can be a Talker and a Listener. If your computer has a National Instruments GPIB interface board and NI-488 software installed, it can function as a Talker, Listener, and Controller.
Controller-In-Charge and System Controller
You can have multiple Controllers on the GPIB, but only one Controller at a time can be the active Controller, or Controller-In-Charge (CIC). The
CIC can either be active or inactive (Standby) Controller. Control can pass from the current CIC to an idle Controller, but only the System Controller, usually a GPIB interface board, can make itself the CIC.
© National Instruments Corporation 1-1 GPIB for VXIpc Controllers and VxWorks
Chapter 1 Introduction
GPIB Addressing
All GPIB devices and boards must be assigned a unique GPIB address.
A GPIB address is made up of two parts: a primary address and an optional secondary address.
The primary address is a number in the range 0 to 30. The GPIB Controller uses this address to form a talk or listen address that is sent over the GPIB when communicating with a device.
A talk address is formed by setting bit 6, the TA (Talk Active) bit of the
GPIB address. A listen address is formed by setting bit 5, the LA (Listen
Active) bit of the GPIB address. For example, if a device is at address 1, the Controller sends hex 41 (address 1 with bit 6 set) to make the device a
Talker. Because the Controller is usually at primary address 0, it sends
hex 20 (address 0 with bit 5 set) to make itself a Listener. Figure 1-1 shows
the configuration of the GPIB address bits.
Bit
Position
Meaning
7
0
6
TA
5 4 3 2 1 0
LA GPIB Primary Address (range 030)
Figure 1-1. GPIB Address Bits
With some devices, you can use secondary addressing. A secondary address is a number in the range hex 60 to hex 7E. When secondary addressing is in use, the Controller sends the primary talk or listen address of the device followed by the secondary address of the device.
Sending Messages across the GPIB
Devices on the bus communicate by sending messages. Signals and lines transfer these messages across the GPIB interface, which consists of
16 signal lines and eight ground return (shield drain) lines. The 16 signal lines are discussed in the following sections
Data Lines
Eight data lines, DIO1 through DIO8, carry both data and command messages.
GPIB for VXIpc Controllers and VxWorks 1-2 © National Instruments Corporation
Chapter 1 Introduction
Handshake Lines
Three hardware handshake lines asynchronously control the transfer of message bytes between devices. This process is a three-wire interlocked handshake, and it guarantees that devices send and receive message bytes
on the data lines without transmission error. Table 1-1 summarizes the
GPIB handshake lines.
Line
NRFD
(not ready for data)
NDAC
(not data accepted)
DAV
(data valid)
Table 1-1. GPIB Handshake Lines
Description
Listening device is ready/not ready to receive a message byte. Also used by the Talker to signal high-speed GPIB transfers.
Listening device has/has not accepted a message byte.
Talking device indicates signals on data lines are stable (valid) data.
Interface Management Lines
Five GPIB hardware lines manage the flow of information across the bus.
Table 1-2 summarizes the GPIB interface management lines.
ATN
Line
(attention)
IFC
(interface clear)
REN
(remote enable)
SRQ
(service request)
EOI
(end or identify)
Table 1-2. GPIB Interface Management Lines
Description
Controller drives ATN true when it sends commands and false when it sends data messages.
System Controller drives the IFC line to initialize the bus and make itself CIC.
System Controller drives the REN line to place devices in remote or local program mode.
Any device can drive the SRQ line to asynchronously request service from the
Controller.
Talker uses the EOI line to mark the end of a data message. Controller uses the EOI line when it conducts a parallel poll.
© National Instruments Corporation 1-3 GPIB for VXIpc Controllers and VxWorks
Chapter 1 Introduction
Setting up and Configuring Your System
Devices are usually connected with a cable assembly consisting of a shielded 24-conductor cable with both a plug and receptacle connector at each end. With this design, you can link devices in a linear configuration,
a star configuration, or a combination of the two. Figure 1-2 shows the
linear and star configurations.
VXIpc Controller VXIpc Controller
Device A
Device A Device D
Device B
Device C a. Linear Configuration
Device B Device C b. Star Configuration
Figure 1-2. Linear and Star System Configuration
Controlling More Than One Board
Figure 1-3 shows an example of a multiboard system configuration.
gpib0 is the access board for the plotter and printer, and gpib1 is the access board for the voltmeter. The control functions of the devices automatically access their respective boards.
GPIB for VXIpc Controllers and VxWorks 1-4 © National Instruments Corporation
Chapter 1 Introduction
Digital
Voltmeter
Plug-in Board
GPIB1
Plotter
VXIpc Controller with built-in GPIB0
Printer
Figure 1-3. Example of Multiboard System Setup
Configuration Requirements
To achieve the high data transfer rate that the GPIB was designed for, you must limit the physical distance between devices and the number of devices on the bus. The following restrictions are typical:
• A maximum separation of four meters between any two devices and an average separation of two meters over the entire bus
• A maximum total cable length of 20 m
• A maximum of 15 devices connected to each bus, with at least two-thirds powered on
For high-speed operation, the following restrictions apply:
• All devices in the system must be powered on
• Cable lengths as short as possible up to a maximum of 15 m of cable for each system
• With at least one equivalent device load per meter of cable
If you want to exceed these limitations, you can use bus extenders to increase the cable length or expanders to increase the number of device loads. Extenders and expanders are available from National Instruments.
© National Instruments Corporation 1-5 GPIB for VXIpc Controllers and VxWorks
2
Developing Your Application with the VxWorks Drivers
This chapter explains how to use the VxWorks GPIB drivers, and how to develop a GPIB application using the NI-488 API.
Using the VxWorks NI-488 and ESP-488 Drivers
The GPIB drivers that come with the VxWorks-based controller provide two different ways to use the GPIB functions. The NI-488 driver is derived from the NI-488DDK, and offers a 100% compatible subset of the full
NI-488 drivers used on other operating systems. The ESP-488 driver gives users of the VXIcpu-030 an easy way to port their existing GPIB programs to newer hardware by providing a mapping of ESP-488 functions to NI-488 functions.
National Instruments strongly recommends you use the ESP-488 driver only for porting applications from the VXIcpu-030 to a new controller. The
ESP-488 driver is merely a mapping of the corresponding NI-488 functions, and using the actual NI-488 functions will make it easier to transfer programs between a VxWorks system and other operating systems that use the standard NI-488 driver. Furthermore, the NI-488 driver offers support for multithreading, which is not available in the ESP-488 driver.
We wish to emphasize that the ESP-488 library is provided only for the convenience of users making the transition from the VXIcpu-030 to a newer controller.
Users of the VXIcpu-030 should note that under certain error conditions, the new ESP-488 library might behave slightly differently from the
ESP-488 library provided with the VXIcpu-030. This is because of the underlying NI-488 driver, but should not adversely affect user code under normal circumstances.
The GPIB library files provided with the VxWorks-based controller are:
• nigpib.o
—the NI-488 library
• espgpib.o
—the ESP-488 library
© National Instruments Corporation 2-1 GPIB for VXIpc Controllers and VxWorks
Chapter 2 Developing Your Application with the VxWorks Drivers
• ibic.o
—the old VXIcpu-030 GPIB interactive control program, which requires the ESP-488 library
• ugpib.h
—the header file for the NI-488 API
• esp488.h
—the header file for the ESP-488 API (refer to Compiling and Linking Your Application
, later in this chapter, for more information about how to use this file)
• ni4882.c
—source code for the 488.2 extensions library
(in util subdirectory)
• ni4882.h
—the header file for 488.2 extensions
(in util subdirectory)
• README.TXT
—a text file with further important information about the
GPIB libraries
Using VxWorks NI-488 Functions
The VxWorks NI-488 functions perform basic GPIB operations. These low-level functions access the interface board directly and require you to handle the addressing and bus management protocol. In addition to serving as a foundation upon which you can implement higher-level functions, these functions give you the flexibility and control to handle situations such as the following:
• Communicating with non-compliant (non-IEEE 488.2) devices
• Altering various low-level board configurations
• Developing non-controller applications
• Managing the bus in non-typical ways
The VxWorks NI-488 functions are completely compatible with the corresponding functions of standard NI-488.2 drivers from National
Instruments.
Items to Include in Your Application
Items you should include in your C application programs are as follows:
• The header file ugpib.h
contains prototypes for the GPIB functions and constants that you can use in your application.
• One or more calls to the ibfind function to obtain a unit descriptor for each GPIB board that the application uses.
• Code to check for errors after each NI-488 function call.
GPIB for VXIpc Controllers and VxWorks 2-2 © National Instruments Corporation
Chapter 2 Developing Your Application with the VxWorks Drivers
• A function to handle GPIB errors. This function takes the board offline and closes the application. If the function is declared as: void gpiberr (char * msg); /*function prototype*/ then your application invokes it as follows: if (ibsta & ERR) { gpiberr("GPIB error");
}
Checking Status with Global Variables
Each NI-488 function updates four global variables to reflect the status of the board that you are using. These global status variables are the status word ( ibsta ), the error variable ( iberr ) and the count variables ( ibcnt and ibcntl ). They contain useful information about the performance of your application. Your application should check these variables after each
GPIB call. The following sections describe each of these global variables and how you can use them in your application.
Status Word (ibsta)
All functions update a global status word, ibsta , which contains information about the state of the GPIB and the GPIB hardware. The value stored in ibsta is the return value of all of the NI-488 functions except ibfind . You can examine various status bits in ibsta and use that information to make decisions about continued processing. If you check for possible errors after each call using the ibsta ERR bit, debugging your application is much easier.
ibsta is an integer-sized value. The least significant 16 bits of ibsta are meaningful. A bit value of one (1) indicates that a certain condition is in effect, and a bit value of zero (0) indicates that the condition is not in effect.
Table 2-1 shows the condition that each bit position represents and the bit
mnemonics. For a detailed explanation of each of the status conditions,
refer to Appendix B, Status Word Conditions .
Mnemonic
ERR
TIMO
Table 2-1. Status Word Layout
Bit Pos.
15
14
Hex
Value
8000
4000
Description
GPIB error
Time limit exceeded
© National Instruments Corporation 2-3 GPIB for VXIpc Controllers and VxWorks
Chapter 2 Developing Your Application with the VxWorks Drivers
CIC
ATN
TACS
LACS
DTAS
DCAS
Mnemonic
END
SRQI
CMPL
LOK
REM
3
2
5
4
1
0
Bit Pos.
13
7
6
12
8
Table 2-1. Status Word Layout (Continued)
2
1
8
4
20
10
Hex
Value
2000
1000
100
80
40
Description
END or EOS detected
SRQ interrupt received
I/O completed
Lockout State
Remote State
Controller-In-Charge
Attention is asserted
Talker
Listener
Device Trigger State
Device Clear State
The application header file ugpib.h
included on your distribution medium defines each of the ibsta status bits. You can test for an ibsta status bit being set using the bitwise and operator ( & in C/C++). For example, the ibsta ERR bit is bit 15 of ibsta . To check for a GPIB error, use the following statement after each GPIB call as shown: if (ibsta & ERR) printf("GPIB error encountered");
Error Variable (iberr)
If the ERR bit is set in ibsta , a GPIB error has occurred. When an error occurs, the error type is specified by the integer iberr . To check for a
GPIB error, use the following statement after each GPIB call: if (ibsta & ERR) printf("GPIB error %d encountered", iberr);
Note The value in iberr is meaningful as an error type only when the ERR bit is set in ibsta , indicating that an error has occurred.
For more information on error codes and solutions refer to the
section later in this chapter, or Appendix C,
GPIB for VXIpc Controllers and VxWorks 2-4 © National Instruments Corporation
Chapter 2 Developing Your Application with the VxWorks Drivers
Count Variables (ibcnt and ibcntl)
The count variables are updated after each read, write, or command function. ibcnt is an integer value and ibcntl is a long integer value. As implemented on most modern systems today, ibcnt and ibcntl are both
32-bit integers. On some older systems, such as MS-DOS, ibcnt is a
16-bit integer; on some newer systems, ibcntl is a 64-bit integer. For cross-platform compatibility, all applications should use ibcntl . If you are reading data, the count variables indicate the number of bytes read. If you are sending data or commands, the count variables reflect the number of bytes sent.
In your application you can use the count variables to null-terminate an
ASCII string of data received from an instrument. For example, if data is received in an array of characters, you can use ibcntl to null-terminate the array and print the measurement on the screen as follows: char rdbuf[512]; ibrd (ud, rdbuf, 20L); if (!(ibsta & ERR)){ rdbuf[ibcntl] = '\0'; printf ("Read: %s\n", rdbuf);
} else { error();
}
Compiling and Linking Your Application
When writing NI-488 or ESP-488 programs, you need to include the appropriate header file, which depends on which GPIB library you are using. Normally, you will use NI-488, and the default setup uses the NI-488 version of ugpib.h
. If you need the ESP-488 API instead, rename the default ugpib.h
to ni488.h
and copy the file esp488.h
to ugpib.h
.
Always use the directive #include “ugpib.h” in your programs, whether they are NI-488 or ESP-488 based.
Compiling a program for either API works no differently from compiling other programs for VxWorks. If you are unfamiliar with VxWorks, the process is very similar to compilation on other systems. You can find detailed information in the Wind River Systems programming documentation. You may find the Intel x86 appendix of the VxWorks
Programmer’s Guide and the gcc/g++ chapter of the GNU Toolkit User’s
Guide particularly helpful.
© National Instruments Corporation 2-5 GPIB for VXIpc Controllers and VxWorks
Chapter 2 Developing Your Application with the VxWorks Drivers
On VxWorks, the functions in the NI-488 (or ESP-488) library are automatically linked into your program as long as the appropriate library is already loaded when you load your NI-488 or ESP-488 application into
VxWorks. To load the library, change to the directory in which the libraries are installed (by default, /ide0 ) and use the command ld < nigpib.o
or ld < espgpib.o
.
Refer to the README.TXT file for more information about the two libraries. As noted at the beginning of this chapter, National Instruments strongly recommends you use the NI-488 driver unless you need the
ESP-488 driver for backward compatibility with the VXIcpu-030.
Debugging Considerations
This section contains typical errors you may encounter and some considerations for debugging your application.
Using the Global Status Variables
After each function call to your NI-488 driver, ibsta , iberr , ibcnt , and ibcntl are updated before the call returns to your application. You should check for an error after each GPIB call. Refer to the
Global Variables section earlier in this chapter for more information about
how to use these variables within your program to automatically check for errors.
After you determine which GPIB call is failing and note the corresponding
values of the global variables, refer to Appendix B, Status Word
, and Appendix C, Error Codes and Solutions . These
appendices can help you interpret the state of the driver.
Configuration Errors
Some applications require customized configuration of the GPIB driver.
For example, you might want to terminate reads on a special end-of-string character, or you might require secondary addressing. In these cases, you can temporarily reconfigure the driver while your application is running using the ibeos and ibsad functions.
Refer to the descriptions of these functions and others in Chapter 3,
Functions , for more information.
GPIB for VXIpc Controllers and VxWorks 2-6 © National Instruments Corporation
Chapter 2 Developing Your Application with the VxWorks Drivers
Timing Errors
In some cases, your application might fail because it is issuing the NI-488 calls too quickly for your device to process and respond to them. This problem can also result in corrupted or incomplete data.
A well behaved IEEE 488 device should hold off handshaking and set the appropriate transfer rate. If your device is not well behaved, you can test for and resolve the timing error by single-stepping through your program and inserting finite delays between each GPIB call. One way to do this is to have your device communicate its status whenever possible. Although this method is not possible with many devices, it is usually the best option. Your delays are controlled by the device and your application can adjust itself and work independently on any platform. Other delay mechanisms might cause varying delay times on different platforms.
Communication Errors
Repeat Addressing
Devices adhering to the IEEE 488.2 standard should remain in their current state until specific commands are sent across the GPIB to change their state. However, some devices require GPIB addressing before any GPIB activity. Therefore, you might need to make additional calls to ibcmd in your application to perform repeat addressing if your device does not remain in its currently addressed state.
Termination Method
You should learn the data termination method that your devices use. By default, your NI-488 software sends EOI on writes and terminates reads on
EOI or a specific byte count. If you send a command string to your device and it does not respond, it might be because it does not recognize the end of the command. You might need to send a termination message such as CR
LF after a write command as follows: ibwrt(ud,"COMMAND\x0D\x0A",9);
© National Instruments Corporation 2-7 GPIB for VXIpc Controllers and VxWorks
3
NI-488 Functions
This chapter lists the NI-488 functions and describes the purpose, format, input and output parameters, and possible errors for each function.
Function Names
The functions in this chapter are listed alphabetically.
Purpose
Each function description includes a brief statement of the purpose of the function.
Format
The format section describes the format of each function in the C programming language.
Input and Output
The input and output parameters for each function are listed. Function Return describes the return value of the function.
Description
The description section gives details about the purpose and effect of each function.
Examples
Some function descriptions include sample code showing how to use the function. For more detailed and complete examples, refer to the source code support files included in the util directory with your VxWorks GPIB software.
© National Instruments Corporation 3-1 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — Possible Errors
Possible Errors
Each function description includes a list of errors that could occur when it is invoked.
List of NI-488 Functions
Function ibcac ibcmd ibeos ibeot ibpad ibppc ibrd ibrpp ibrsc ibrsv ibsad ibsic ibfind ibgts ibist iblines ibln ibloc ibonl
The following table contains an alphabetical list of the VxWorks NI-488 functions.
Table 3-1. NI-488 Functions
Purpose
Become Active Controller
Send GPIB commands
Configure the end-of-string (EOS) termination mode or character
Enable or disable the automatic assertion of the GPIB EOI line at the end of write I/O operations
Open and initialize a GPIB board
Go from Active Controller to Standby
Set or clear the board individual status bit for parallel polls
Return the status of the eight GPIB control lines
Check for the presence of a device on the bus
Go to local
Place the interface board online or offline
Change the primary address
Parallel poll configure
Read data into a user buffer
Conduct a parallel poll
Request or release system control
Request service and change the serial poll status byte
Change or disable the secondary address
Assert interface clear
GPIB for VXIpc Controllers and VxWorks 3-2 © National Instruments Corporation
Chapter 3 NI-488 Functions — List of NI-488 Functions
Function ibsre ibtmo ibwait ibwrt
Table 3-1. NI-488 Functions (Continued)
Purpose
Set or clear the Remote Enable (REN) line
Change or disable the I/O timeout period
Wait for GPIB events
Write data from a user buffer
© National Instruments Corporation 3-3 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — IBCAC
IBCAC
Purpose
Become Active Controller.
Format int ibcac (int ud, int v)
Input ud v
A board unit descriptor
Determines if control is to be taken asynchronously or synchronously
Output
Function Return
Possible Errors
EARG
ECIC
EDVR
ENEB
The value of ibsta
Description
Using ibcac , the designated GPIB board attempts to become the Active Controller by asserting ATN. If v is zero, the GPIB board takes control asynchronously; if v is non-zero, the GPIB board takes control synchronously. Before you call ibcac , the GPIB board must already be CIC. To make the board CIC, use the ibsic function.
To take control synchronously, the GPIB board attempts to assert the ATN signal without corrupting transferred data. If this is not possible, the board takes control asynchronously.
To take control asynchronously, the GPIB board asserts ATN immediately without regard for any data transfer currently in progress.
Most applications do not need to use ibcac . Functions that require ATN to be asserted, such as ibcmd , do so automatically.
ud is valid but does not refer to an interface board.
The interface board is not Controller-In-Charge.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
GPIB for VXIpc Controllers and VxWorks 3-4 © National Instruments Corporation
Chapter 3 NI-488 Functions — IBCMD
IBCMD
Purpose
Send GPIB commands.
Format int ibcmd (int ud, void *cmdbuf, long count)
Input ud cmdbuf count
Output
Function Return
A board unit descriptor
Buffer of command bytes to send
Number of command bytes to send
Possible Errors
EABO
EARG
ECIC
EDVR
ENEB
ENOL
The value of ibsta
Description ibcmd sends count bytes from cmdbuf over the GPIB as command bytes (interface messages). The number of command bytes transferred is returned in the global variable, ibcntl
. Refer to Appendix A, Multiline Interface Messages , for a table of the defined
interface messages.
Command bytes configure the state of the GPIB, such as addressing devices to listen or talk.
The timeout period expired before all of the command bytes were sent.
ud is valid but does not refer to an interface board.
The interface board is not Controller-In-Charge.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
No Listeners are on the GPIB.
© National Instruments Corporation 3-5 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — IBEOS
IBEOS
Purpose
Configure the end-of-string (EOS) termination mode or character.
Format int ibeos (int ud, int v)
Input ud v
Output
Function Return
Board descriptor
EOS mode and character information
The value of ibsta
Description ibeos configures the EOS termination mode or EOS character for the board. The parameter v describes the new end-of-string (EOS) configuration to use. If v is zero, then the EOS configuration is disabled. Otherwise, the low byte is the EOS character and the upper byte contains flags which define the EOS mode.
Note Defining an EOS byte does not cause the driver to automatically send that byte at the end of write I/O. Your application is responsible for placing the EOS byte at the end of the data strings that it defines.
Table 3-2 describes the different EOS configurations and the corresponding values of
v . If no error occurs during the call, the value of the previous EOS setting is returned in iberr .
Bit
A
B
C
Table 3-2. EOS Configurations
Configuration
Terminate read when EOS is detected.
Set EOI with EOS on write function.
Compare all 8 bits of EOS byte rather than low 7 bits (all read and write functions).
Value of v
High Byte Low Byte
00000100
00001000
00010000
EOS character
EOS character
EOS character
GPIB for VXIpc Controllers and VxWorks 3-6 © National Instruments Corporation
Chapter 3 NI-488 Functions — IBEOS
Configuration bits A and C determine how to terminate read I/O operations. If bit A is set and bit C is clear, then a read ends when a byte that matches the low seven bits of the EOS character is received. If bits A and C are both set, then a read ends when a byte that matches all eight bits of the EOS character is received.
Configuration bits B and C determine when a write I/O operation asserts the GPIB EOI line.
If bit B is set and bit C is clear, then EOI is asserted when the written character matches the low seven bits of the EOS character. If bits B and C are both set, then EOI is asserted when the written character matches all eight bits of the EOS character.
For more information on the termination of I/O operations, refer to Chapter 4, GPIB
.
Examples ibeos (ud, 0x140A); /* Configure the software to end reads on
newline character (hex 0A) for the unit
descriptor, ud */ ibeos (ud, 0x180A); /* Configure the software to assert the GPIB
EOI line whenever the newline character
(hex 0A) is written out by the unit
descriptor, ud */
Possible Errors
EARG
EDVR
ENEB
The high byte of v contains invalid bits.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
© National Instruments Corporation 3-7 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — IBEOT
IBEOT
Purpose
Enable or disable the automatic assertion of the GPIB EOI line at the end of write I/O operations.
Format int ibeot (int ud, int v)
Input ud v
Output
Function Return
Board descriptor
Enables or disables the end of transmission assertion of EOI
Possible Errors
EDVR
ENEB
The value of ibsta
Description ibeot enables or disables the assertion of the EOI line at the end of write I/O operations for the board ud describes. If v is non-zero, then EOI is asserted when the last byte of a GPIB write is sent. If v is zero, then nothing occurs when the last byte is sent. If no error occurs during the call, then the previous value of EOT is returned in iberr .
For more information on the termination of I/O operations, refer to Chapter 4, GPIB
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
GPIB for VXIpc Controllers and VxWorks 3-8 © National Instruments Corporation
Chapter 3 NI-488 Functions — IBFIND
IBFIND
Purpose
Open and initialize a GPIB board descriptor.
Format int ibfind (char *udname)
Input udname
Output
Function Return
ENEB
A GPIB board name
The board descriptor, or -1
Description ibfind acquires a descriptor for a GPIB board; this board descriptor can be used in subsequent NI-488 functions.
ibfind performs the equivalent of an ibonl 1 to initialize the board descriptor. The unit descriptor that ibfind returns remains valid until you use ibonl 0 to put the board offline.
If ibfind is unable to get a valid descriptor, -1 is returned; the ERR bit is set in ibsta and iberr contains EDVR.
Possible Errors
EDVR Either udname is not recognized as a board name or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
© National Instruments Corporation 3-9 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — IBGTS
IBGTS
Purpose
Go from Active Controller to Standby.
Format int ibgts (int ud, int v)
Input ud v
Output
Function Return
EARG
ECIC
EDVR
ENEB
Board descriptor
Determines whether to perform acceptor handshaking
The value of ibsta
Description ibgts causes the GPIB board at ud to go to Standby Controller and the GPIB ATN line to be unasserted. If v is non-zero, acceptor handshaking or shadow handshaking is performed until
END occurs or until ATN is reasserted by a subsequent ibcac call. With this option, the GPIB board can participate in data handshake as an acceptor without actually reading data. If END is detected, the interface board enters a Not Ready For Data (NRFD) handshake holdoff state which results in hold off of subsequent GPIB transfers. If v is 0, no acceptor handshaking or holdoff is performed.
Before performing an ibgts with shadow handshake, call the ibeos function to establish proper EOS modes.
For details on the IEEE-488.1 handshake protocol, refer to ANSI/IEEE Standard 488.1-1987,
IEEE Standard Digital Interface for Programmable Instrumentation.
Possible Errors
EADR v is non-zero, and either ATN is low or the interface board is a Talker or
Listener.
ud is valid but does not refer to an interface board.
The interface board is not Controller-In-Charge.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
GPIB for VXIpc Controllers and VxWorks 3-10 © National Instruments Corporation
Chapter 3 NI-488 Functions — IBIST
IBIST
Purpose
Set or clear the board individual status bit for parallel polls.
Format int ibist (int ud, int v)
Input ud v
Output
Function Return
Board descriptor
Indicates whether to set or clear the ist bit
Possible Errors
EARG
EDVR
ENEB
The value of ibsta
Description ibist sets the interface board ist (individual status) bit according to v . If v is zero, the ist bit is cleared; if v is non-zero, the ist bit is set. The previous value of the ist bit is returned in iberr .
For more information on parallel polling, refer to Chapter 4, GPIB Programming Techniques .
ud is valid but does not refer to an interface board.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
© National Instruments Corporation 3-11 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — IBLINES
IBLINES
Purpose
Return the status of the eight GPIB control lines.
Format int iblines (int ud, short *clines)
Input ud Board descriptor
Output clines
Function Return
Returns GPIB control line state information
The value of ibsta
Description iblines returns the state of the GPIB control lines in clines . The low-order byte (bits 0 through 7) of clines contains a mask indicating the capability of the GPIB interface board to sense the status of each GPIB control line. The upper byte (bits 8 through 15) contains the
GPIB control line state information. The following is a pattern of each byte.
7
EOI
6
ATN
5
SRQ
4
REN
3
IFC
2
NRFD
1
NDAC
0
DAV
To determine if a GPIB control line is asserted, first check the appropriate bit in the lower byte to determine if the line can be monitored. If the line can be monitored (indicated by a 1 in the appropriate bit position), then check the corresponding bit in the upper byte. If the bit is set
(1), the corresponding control line is asserted. If the bit is clear (0), the control line is unasserted.
Example short lines; iblines (ud, &lines); if (lines & ValidREN) { /* check to see if REN is asserted */ if (lines & BusREN) { printf ("REN is asserted");
}
}
GPIB for VXIpc Controllers and VxWorks 3-12 © National Instruments Corporation
Chapter 3 NI-488 Functions — IBLINES
Possible Errors
EARG
EDVR
ENEB ud is valid but does not refer to an interface board.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
© National Instruments Corporation 3-13 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — IBLN
IBLN
Purpose
Check for the presence of a device on the bus.
Format int ibln (int ud, int pad, int sad, short *listen)
Input ud pad sad
Output listen
Function Return
Board descriptor
The primary GPIB address of the device
The secondary GPIB address of the device
Possible Errors
EARG
ECIC
EDVR
ENEB
Indicates if a device is present or not
The value of ibsta
Description ibln determines whether there is a listening device at the GPIB address designated by the pad and sad parameters. If a Listener is detected, a non-zero value is returned in listen .
If no Listener is found, zero is returned.
The pad parameter can be any valid primary address (a value between 0 and 30). The sad parameter can be any valid secondary address (a value between 96 to 126), or one of the constants NO_SAD or ALL_SAD . The constant NO_SAD designates that no secondary address is to be tested (only a primary address is tested). The constant ALL_SAD designates that all secondary addresses are to be tested.
Either the pad or sad argument is invalid.
The interface board is not Controller-In-Charge.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
GPIB for VXIpc Controllers and VxWorks 3-14 © National Instruments Corporation
Chapter 3 NI-488 Functions — IBLOC
IBLOC
Purpose
Go to Local.
Format int ibloc (int ud)
Input ud
Output
Function Return
Board descriptor
Possible Errors
EDVR
ENEB
The value of ibsta
Description ibloc places the board in local mode if it is not in a lockout state. The board is in a lockout state if LOK appears in the status word ibsta . If the board is in a lockout state, the call has no effect.
The ibloc function is used to simulate a front panel RTL (Return to Local) switch if the computer is used as an instrument.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
© National Instruments Corporation 3-15 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — IBONL
IBONL
Purpose
Place the interface board online or offline.
Format int ibonl (int ud, int v)
Input ud v
Output
Function Return
Board descriptor
Indicates whether the board is to be taken online or offline
Possible Errors
EDVR
ENEB
The value of ibsta
Description ibonl resets the board and places all its software configuration parameters in their pre-configured state. In addition, if v is zero, the interface board is taken offline. If v is non-zero, the interface board is left operational, or online.
If an interface board is taken offline, the board descriptor ( ud ) is no longer valid. You must execute an ibfind to access the board again.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
GPIB for VXIpc Controllers and VxWorks 3-16 © National Instruments Corporation
Chapter 3 NI-488 Functions — IBPAD
IBPAD
Purpose
Change the primary address.
Format int ibpad (int ud, int v)
Input ud v
Board descriptor
GPIB primary address
Output
Function Return
Possible Errors
EARG
EDVR
ENEB
The value of ibsta
Description ibpad sets the primary GPIB address of the board to v , an integer ranging from 0 to 30. If no error occurs during the call, then iberr contains the previous GPIB primary address.
v is not a valid primary GPIB address; it must be in the range 0 to 30.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
© National Instruments Corporation 3-17 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — IBPPC
IBPPC
Purpose
Parallel poll configure.
Format int ibppc (int ud, int v)
Input ud v
Output
Function Return
Board descriptor
Parallel poll enable/disable value
Possible Errors
EARG
EDVR
ENEB
The value of ibsta
Description ibppc performs a local parallel poll configuration on the interface board using the parallel poll configuration value v . Valid parallel poll messages are 96 to 126 (hex 60 to hex 7E) or zero to send PPD. If no error occurs during the call, then iberr contains the previous value of the local parallel poll configuration.
For more information on parallel polling, refer to Chapter 4, GPIB Programming Techniques .
v does not contain a valid PPE or PPD message.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
GPIB for VXIpc Controllers and VxWorks 3-18 © National Instruments Corporation
Chapter 3 NI-488 Functions — IBRD
IBRD
Purpose
Read data into a user buffer.
Format int ibrd (int ud, void *rdbuf, long count)
Input ud count
Board descriptor
Number of bytes to be read from the GPIB
Output rdbuf
Function Return
Possible Errors
EABO
EADR
EDVR
ENEB
Address of buffer into which data is read
The value of ibsta
Description ibrd reads up to count bytes of data and places the data into the buffer specified by rdbuf . ibrd assumes that the GPIB is already properly addressed. The operation terminates normally when count bytes have been received or END is received. The operation terminates with an error if the transfer could not complete within the timeout period or, if the board is not CIC, the CIC sends a Device clear on the GPIB. The actual number of bytes transferred is returned in the global variable ibcntl .
Either count bytes or END was not received within the timeout period or a
Device Clear message was received after the read operation began.
The GPIB is not correctly addressed; use ibcmd to address the GPIB.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
© National Instruments Corporation 3-19 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — IBRPP
IBRPP
Purpose
Conduct a parallel poll.
Format int ibrpp (int ud, char *ppr)
Input ud
Output ppr
Function Return
Board descriptor
Possible Errors
ECIC
EDVR
ENEB
Parallel poll response byte
The value of ibsta
Description ibrpp parallel polls all the devices on the GPIB. The result of this poll is returned in ppr .
For more information on parallel polling, refer to Chapter 4, GPIB Programming Techniques .
The interface board is not Controller-In-Charge.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
GPIB for VXIpc Controllers and VxWorks 3-20 © National Instruments Corporation
Chapter 3 NI-488 Functions — IBRSC
IBRSC
Purpose
Request or release system control.
Format int ibrsc (int ud, int v)
Input ud v
Board descriptor
Determines if system control is to be requested or released
Output
Function Return
Possible Errors
EARG
EDVR
ENEB
The value of ibsta
Description ibrsc requests or releases the capability to send Interface Clear (IFC) and Remote Enable
(REN) messages. If v is zero, the board releases system control, and functions requiring
System Controller capability are not allowed. If v is non-zero, functions requiring System
Controller capability are subsequently allowed. If no error occurs during the call, then iberr contains the previous System Controller state of the board.
ud is a valid descriptor but does not refer to a board.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
© National Instruments Corporation 3-21 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — IBRSV
IBRSV
Purpose
Request service and change the serial poll status byte.
Format int ibrsv (int ud, int v)
Input ud v
Output
Function Return
Board descriptor
Serial poll status byte
Possible Errors
EARG
EDVR
ENEB
The value of ibsta
Description ibrsv is used to request service from the Controller and to provide the Controller with an application-dependent status byte when the Controller serial polls the GPIB board.
The value v is the status byte that the GPIB board returns when serial polled by the
Controller-In-Charge. If bit 6 (hex 40) is set in v , the GPIB board requests service from the
Controller by asserting the GPIB SRQ line. When ibrsv is called and an error does not occur, the previous status byte is returned in iberr .
ud is a valid descriptor but does not refer to a board.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
GPIB for VXIpc Controllers and VxWorks 3-22 © National Instruments Corporation
Chapter 3 NI-488 Functions — IBSAD
IBSAD
Purpose
Change or disable the secondary address.
Format int ibsad (int ud, int v)
Input ud v
Board descriptor
GPIB secondary address
Output
Function Return
Possible Errors
EARG
EDVR
ENEB
The value of ibsta
Description ibsad changes the secondary GPIB address of the given board to v , an integer in the range
96 to 126 (hex 60 to hex 7E) or zero. If v is zero, secondary addressing is disabled. If no error occurs during the call, then the previous value of the GPIB secondary address is returned in iberr .
v is non-zero and outside the legal range 96 to 126.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
© National Instruments Corporation 3-23 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — IBSIC
IBSIC
Purpose
Assert interface clear.
Format int ibsic (int ud)
Input ud
Output
Function Return
Board descriptor
Possible Errors
EARG
EDVR
ENEB
ESAC
The value of ibsta
Description ibsic asserts the GPIB interface clear (IFC) line for at least 100
µ s if the GPIB board is
System Controller. This initializes the GPIB and makes the interface board CIC and Active
Controller with ATN asserted.
The IFC signal resets only the GPIB interface functions of bus devices and not the internal device functions. Consult your device documentation to determine how to reset the internal functions of your device.
ud is a valid descriptor but does not refer to a board.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
The board does not have System Controller capability.
GPIB for VXIpc Controllers and VxWorks 3-24 © National Instruments Corporation
Chapter 3 NI-488 Functions — IBSRE
IBSRE
Purpose
Set or clear the Remote Enable line.
Format int ibsre (int ud, int v)
Input ud v
Output
Function Return
Board descriptor
Indicates whether to set or clear the REN line
Possible Errors
EARG
EDVR
ENEB
ESAC
The value of ibsta
Description
If v is non-zero, the GPIB Remote Enable (REN) line is asserted. If v is zero, REN is unasserted. The previous value of REN is returned in iberr .
Devices use REN to choose between local and remote modes of operation. A device should not actually enter remote mode until it receives its listen address.
ud is a valid descriptor but does not refer to a board.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
The board does not have System Controller capability.
© National Instruments Corporation 3-25 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — IBTMO
IBTMO
Purpose
Change or disable the timeout period.
Format int ibtmo (int ud, int v)
Input ud v
Output
Function Return
Board descriptor
Timeout duration code
The value of ibsta
Description ibtmo sets the timeout period of the board to v . The timeout period is used to select the maximum duration allowed for an I/O operation (for example, ibrd and ibwrt ) or for an ibwait operation with TIMO in the wait mask. If the operation does not complete before the timeout period elapses, then the operation is aborted and TIMO is returned in ibsta . See
Table 3-3 for a list of valid timeout values. These timeout values represent the minimum
timeout period. The actual period may be longer.
TNONE
T10us
T30us
T100us
T300us
T1ms
T3ms
T10ms
T30ms
T100ms
Constant
Table 3-3. Timeout Code Values
Value of v
0
1
2
5
6
3
4
7
8
9
Minimum Timeout disabled/no timeout
10
30
100
300
1 ms
3 ms
10 ms
30 ms
100 ms
GPIB for VXIpc Controllers and VxWorks 3-26 © National Instruments Corporation
Chapter 3 NI-488 Functions — IBTMO
T300ms
T1s
T3s
T10s
T30s
T100s
T300s
T1000s
Constant
Table 3-3. Timeout Code Values (Continued)
Value of v
10
11
12
13
14
15
16
17
Minimum Timeout
300 ms
1 s
3 s
10 s
30 s
100 s
300 s
1000 s
Possible Errors
EARG
EDVR
ENEB v is invalid.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
© National Instruments Corporation 3-27 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — IBWAIT
IBWAIT
Purpose
Wait for GPIB events.
Format int ibwait (int ud, int mask)
Input ud mask
Output
Function Return
Board descriptor
Bit mask of GPIB events to wait for
The value of ibsta
Description ibwait monitors the events that mask specifies and delays processing until one or more of the events occurs. If the wait mask is zero, ibwait returns immediately with the updated ibsta status word. If TIMO is set in the wait mask, ibwait returns when the timeout period has elapsed, if one or more of the other specified events have not already occurred. If TIMO is not set in the wait mask, then ibwait waits indefinitely for one or more of the specified events to occur. The existing ibwait mask bits are identical to the ibsta bits, and they are
described in Table 3-4. You can configure the timeout period using the
ibtmo function.
Mnemonic
TIMO
END
SRQI
CMPL
LOK
REM
CIC
ATN
Bit Pos.
14
6
5
4
8
7
13
12
40
20
10
2000
1000
100
80
Table 3-4. Wait Mask Layout
Hex
Value
4000 Use the timeout period (see the wait period
Description ibtmo
END or EOS is detected
SRQ is asserted
I/O completed
GPIB board is in Lockout State
GPIB board is in Remote State
GPIB board is CIC
Attention is asserted
) to limit
GPIB for VXIpc Controllers and VxWorks 3-28 © National Instruments Corporation
Chapter 3 NI-488 Functions — IBWAIT
Mnemonic
TACS
LACS
DTAS
DCAS
Bit Pos.
3
2
1
0
Table 3-4. Wait Mask Layout (Continued)
Hex
Value
8
4
2
1
Description
GPIB board is Talker
GPIB board is Listener
GPIB board is in Device Trigger State
GPIB board is in Device Clear State
Possible Errors
EARG
EDVR
ENEB
The bit set in mask is invalid.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
© National Instruments Corporation 3-29 GPIB for VXIpc Controllers and VxWorks
Chapter 3 NI-488 Functions — IBWRT
IBWRT
Purpose
Write data from a user buffer.
Format int ibwrt (int ud, void *wrtbuf, long count)
Input ud wrtbuf count
Board descriptor
Address of the buffer containing the bytes to write
Number of bytes to be written
Output
Function Return
Possible Errors
EABO
EADR
EDVR
ENEB
ENOL
The value of ibsta
Description ibwrt writes count bytes of data from the buffer specified by wrtbuf ; ibwrt assumes that the GPIB is already properly addressed. The operation terminates normally when count bytes have been sent. The operation terminates with an error if count bytes could not be sent within the timeout period or, if the board is not CIC, the CIC sends Device Clear on the GPIB.
The actual number of bytes transferred is returned in the global variable ibcntl .
Either count bytes were not sent within the timeout period, or a Device Clear message was received after the write operation began.
The GPIB is not correctly addressed; use ibcmd to address the GPIB.
Either ud is invalid or the NI-488 driver is not installed.
The interface board is not installed or is not properly configured.
No Listeners were detected on the bus.
GPIB for VXIpc Controllers and VxWorks 3-30 © National Instruments Corporation
4
GPIB Programming Techniques
This chapter describes techniques for using some NI-488 functions in your application.
For more detailed information about each function, refer to Chapter 3,
Termination of Data Transfers
GPIB data transfers are terminated either when the GPIB EOI line is asserted with the last byte of a transfer or when a preconfigured end-of-string (EOS) character is transmitted. By default, the NI-488 driver asserts EOI with the last byte of writes and the EOS modes are disabled.
You can use the ibeot function to enable or disable the end of transmission
(EOT) mode. If EOT mode is enabled, the NI-488 driver asserts the GPIB
EOI line when the last byte of a write is sent out on the GPIB. If it is disabled, the EOI line is not asserted with the last byte of a write.
You can use the ibeos function to enable, disable, or configure the EOS modes. EOS mode configuration includes the following information:
• A 7-bit or 8-bit EOS byte
• EOS comparison method—This indicates whether the EOS byte has seven or eight significant bits. For a 7-bit EOS byte, the eighth bit of the EOS byte is ignored.
• EOS write method—If you enable this, the NI-488 driver automatically asserts the GPIB EOI line when the EOS byte is written to the GPIB. If the buffer passed into an ibwrt call contains five occurrences of the EOS byte, the EOI line is asserted as each of the five
EOS bytes are written to the GPIB. If an ibwrt buffer does not contain an occurrence of the EOS byte, the EOI line is not asserted (unless the
EOT mode is enabled, in which case the EOI line is asserted with the last byte of the write).
• EOS read method—If you enable this, the NI-488 driver terminates ibrd calls when the EOS byte is detected on the GPIB or when the
GPIB EOI line is asserted or when the specified count is reached. If
© National Instruments Corporation 4-1 GPIB for VXIpc Controllers and VxWorks
Chapter 4 GPIB Programming Techniques you disable the EOS read method, ibrd calls terminate only when the
GPIB EOI line is asserted or the specified count has been read.
Waiting for GPIB Conditions
You can use the ibwait function to obtain the current ibsta value or to suspend your application until a specified condition occurs on the GPIB. If you use ibwait with a parameter of zero, it immediately updates ibsta and returns. If you want to use ibwait to wait for one or more events to occur, then pass a wait mask to the function. The wait mask should always include the TIMO event; otherwise, your application is suspended indefinitely until one of the wait mask events occurs.
Talker/Listener Applications
Although designed for Controller-In-Charge applications, you can also use the NI-488 software in most non-Controller situations. These situations are known as Talker/Listener applications because the interface board is not the GPIB Controller.
A Talker/Listener application typically uses ibwait with a mask of 0 to monitor the status of the interface board. Then, based on the status bits set in ibsta , the application takes whatever action is appropriate. For example, the application could monitor the status bits TACS (Talker Active
State) and LACS (Listener Active State) to determine when to send data to or receive data from the Controller. The application could also monitor the
DCAS (Device Clear Active State) and DTAS (Device Trigger Active
State) bits to determine if the Controller has sent the device clear (DCL or
SDC) or trigger (GET) messages to the interface board. If the application detects a device clear from the Controller, it might reset the internal state of message buffers. If it detects a trigger message from the Controller, the application might begin an operation such as taking a voltage reading if the application is actually acting as a voltmeter.
Serial Polling
You can use serial polling to obtain specific information from GPIB devices when they request service. When the GPIB SRQ line is asserted, it signals the Controller that a service request is pending. The Controller must then determine which device asserted the SRQ line and respond accordingly. The most common method for SRQ detection and servicing
GPIB for VXIpc Controllers and VxWorks 4-2 © National Instruments Corporation
Chapter 4 GPIB Programming Techniques is the serial poll. This section describes how you can set up your application to detect and respond to service requests from GPIB devices.
Service Requests from IEEE 488 Devices
IEEE 488 devices request service from the GPIB Controller by asserting the GPIB SRQ line. When the Controller acknowledges the SRQ, it serial polls each open device on the bus to determine which device requested service. Any device requesting service returns a status byte with bit 6 set and then unasserts the SRQ line. Devices not requesting service return a status byte with bit 6 cleared. Manufacturers of IEEE 488 devices use lower order bits to communicate the reason for the service request or to summarize the state of the device.
Service Requests from IEEE 488.2 Devices
The IEEE 488.2 standard refined the bit assignments in the status byte. In addition to setting bit 6 when requesting service, IEEE 488.2 devices also use two other bits to specify their status. Bit 4, the Message Available bit
(MAV), is set when the device is ready to send previously queried data.
Bit 5, the Event Status bit (ESB), is set if one or more of the enabled
IEEE 488.2 events occurs. These events include power-on, user request, command error, execution error, device dependent error, query error, request control, and operation complete. The device can assert SRQ when
ESB or MAV are set, or when a manufacturer-defined condition occurs.
SRQ and Serial Polling with NI-488 Functions
The 488.2 application library included with the NI-488 driver contains some high-level routines that you can use to conduct SRQ servicing and serial polling. Routines pertinent to SRQ servicing and serial polling are ni4882_ReadStatusByte , ni4882_TestSRQ , and ni4882_WaitSRQ .
ni4882_ReadStatusByte serial polls a single device and returns its status byte.
ni4882_TestSRQ determines whether the SRQ line is asserted or unasserted, and returns to the caller immediately.
ni4882_WaitSRQ is similar to ni4882_TestSRQ , except that ni4882_WaitSRQ suspends the application until either SRQ is asserted or the timeout period is exceeded.
© National Instruments Corporation 4-3 GPIB for VXIpc Controllers and VxWorks
Chapter 4 GPIB Programming Techniques
You can also use the IEEE 488.2 routines mentioned in this section to construct your own SRQ servicing routines using the low-level functions of the NI-488 driver. Refer to the file ni4882.c
for more information.
Parallel Polling
Although parallel polling is not widely used, it is a useful method for obtaining the status of more than one device at the same time. The advantage of parallel polling is that a single parallel poll can easily check up to eight individual devices at once. In comparison, eight separate serial polls would be required to check eight devices for their serial poll response bytes. The value of the individual status bit ( ist ) determines the parallel poll response.
Implementing a Parallel Poll with NI-488 Functions
Follow these steps to implement parallel polling using NI-488 functions.
Each step contains example code.
1.
Configure the device for parallel polling using the ibcmd function, unless the device can configure itself for parallel polling.
Parallel poll configuration requires an 8-bit value to designate the data line number, the ist sense, and whether or not the function configures or unconfigures the device for the parallel poll. The bit pattern is as follows:
0 1 1 E S D2 D1 D0
E is 1 to disable parallel polling and 0 to enable parallel polling for that particular device.
S is 1 if the device is to assert the assigned data line when ist = 1 , and 0 if the device is to assert the assigned data line when ist = 0 .
D2 through D0 determine the number of the assigned data line. The physical line number is the binary line number plus one. For example,
DIO3 has a binary bit pattern of 010.
The following example code configures a device at primary address 3 for parallel polling using NI-488 functions. The device asserts DIO7 if its ist bit = 0 , therefore, 0110 0110 (hex 66) is the parallel poll configuration byte.
#include "ugpib.h" char ppr; ud = ibfind("gpib0"); ibsic(ud); ibcmd(ud, "?#\x05\x66", 4);
GPIB for VXIpc Controllers and VxWorks 4-4 © National Instruments Corporation
Chapter 4 GPIB Programming Techniques
If the GPIB interface board configures itself for a parallel poll, you should use the ibppc function. Pass the board unit descriptor value as the first argument in ibppc . In addition, if the individual status bit
( ist ) of the board needs to be changed, use the ibist function.
In the following example, the GPIB board is to configure itself to participate in a parallel poll. It asserts DIO5 when ist = 1 if a parallel poll is conducted.
ibppc(ud, 0x6C); ibist(ud, 1);
2.
Conduct the parallel poll using ibrpp and check the response for a certain value. The following example code performs the parallel poll and compares the response to hex 10, which corresponds to DIO5. If that bit is set, the ist of the device is 1.
ibrpp(ud, &ppr); if (ppr & 0x10) printf("ist = 1\n");
3.
Unconfigure the device for parallel polling with ibcmd . Notice that any value having the parallel poll disable bit set (bit 4) in the bit pattern disables the configuration, so you can use any value between hex 70 and 7E.
ibcmd(ud,"?#\x05\x70", 4);
© National Instruments Corporation 4-5 GPIB for VXIpc Controllers and VxWorks
A
Multiline Interface Messages
This appendix contains a multiline interface message reference list, which describes the mnemonics and messages that correspond to the interface functions. These multiline interface messages are sent and received with
ATN asserted.
For more information on these messages, refer to the ANSI/IEEE
Standard 488.1-1987, IEEE Standard Digital Interface for Programmable
Instrumentation.
© National Instruments Corporation A-1 GPIB for VXIpc Controllers and VxWorks
Appendix A Multiline Interface Messages
26
27
28
29
22
23
24
25
30
31
18
19
20
21
14
15
16
17
10
11
12
13
8
9
6
7
4
5
2
3
Dec
0
1
1A
1B
1C
1D
16
17
18
19
1E
1F
12
13
14
15
0E
0F
10
11
0A
0B
0C
0D
06
07
08
09
02
03
04
05
Hex
00
01
SUB
ESC
FS
GS
SYN
ETB
CAN
EM
RS
US
SO
SI
DLE
DC1
DC2
DC3
DC4
NAK
LF
VT
FF
CR
ACK
BEL
BS
HT
ASCII
NUL
SOH
STX
ETX
EOT
ENQ
Table A-1. Multiline Interface Messages
Msg
GTL
SDC
PPC
GET
TCT
LLO
DCL
PPU
SPE
SPD
CFE
3A
3B
3C
3D
36
37
38
39
3E
3F
32
33
34
35
2E
2F
30
31
2A
2B
2C
2D
26
27
28
29
22
23
24
25
Hex
20
21
58
59
60
61
54
55
56
57
62
63
50
51
52
53
46
47
48
49
42
43
44
45
38
39
40
41
34
35
36
37
Dec
32
33
<
=
;
:
>
?
8
9
6
7
4
5
2
3
0
1
/
.
,
-
*
+
(
)
'
&
"
#
$
%
ASCII
SP
!
MLA24
MLA25
MLA26
MLA27
MLA28
MLA29
MLA30
UNL
MLA16
MLA17
MLA18
MLA19
MLA20
MLA21
MLA22
MLA23
MLA8
MLA9
MLA10
MLA11
MLA12
MLA13
MLA14
MLA15
MLA0
MLA1
MLA2
MLA3
MLA4
MLA5
MLA6
MLA7
Msg
GPIB for VXIpc Controllers and VxWorks A-2 © National Instruments Corporation
Appendix A Multiline Interface Messages
90
91
92
93
86
87
88
89
94
95
82
83
84
85
78
79
80
81
74
75
76
77
70
71
72
73
66
67
68
69
Dec
64
65
5A
5B
5C
5D
56
57
58
59
5E
5F
52
53
54
55
4E
4F
50
51
4A
4B
4C
4D
46
47
48
49
42
43
44
45
Hex
40
41
\
]
Z
[
^
_
X
Y
V
W
T
U
R
S
P
Q
N
O
J
K
L
M
H
I
F
G
D
E
B
C
ASCII
@
A
Table A-1. Multiline Interface Messages (Continued)
MTA22
MTA23
MTA24
MTA25
MTA26
MTA27
MTA28
MTA29
MTA30
UNT
MTA14
MTA15
MTA16
MTA17
MTA18
MTA19
MTA20
MTA21
MTA6
MTA7
MTA8
MTA9
MTA10
MTA11
MTA12
MTA13
Msg
MTA0
MTA1
MTA2
MTA3
MTA4
MTA5
7A
7B
7C
7D
76
77
78
79
7E
7F
72
73
74
75
6E
6F
70
71
6A
6B
6C
6D
66
67
68
69
62
63
64
65
Hex
60
61
122
123
124
125
118
119
120
121
126
127
114
115
116
117
110
111
112
113
106
107
108
109
102
103
104
105
98
99
100
101
Dec
96
97
|
} z
{ x y v w
~
DEL t u r s p q n o l m j k i h f g d e b c
ASCII
` a
Msg
MSA0, PPE
MSA1, PPE, CFG1
MSA2, PPE, CFG2
MSA3, PPE, CFG3
MSA4, PPE, CFG4
MSA5, PPE, CFG5
MSA6, PPE, CFG6
MSA7, PPE, CFG7
MSA8, PPE, CFG8
MSA9, PPE, CFG9
MSA10, PPE, CFG10
MSA11, PPE, CFG11
MSA12, PPE, CFG12
MSA13, PPE, CFG13
MSA14, PPE, CFG14
MSA15, PPE, CFG15
MSA16, PPD
MSA17, PPD
MSA18, PPD
MSA19, PPD
MSA20, PPD
MSA21, PPD
MSA22, PPD
MSA23, PPD
MSA24, PPD
MSA25, PPD
MSA26, PPD
MSA27, PPD
MSA28, PPD
MSA29, PPD
MSA30, PPD
© National Instruments Corporation A-3 GPIB for VXIpc Controllers and VxWorks
Appendix A Multiline Interface Messages
Multiline Interface Message Definitions
CFE † Configuration Enable
CFG † Configure
DCL
GET
Device Clear
Group Execute Trigger
GTL
LLO
MLA
MSA
MTA
PPC
Go To Local
Local Lockout
My Listen Address
My Secondary Address
My Talk Address
Parallel Poll Configure
P P D
P P E
P P U
S D C
S P D
S P E
T C T
U N L
U N T
Parallel Poll Disable
Parallel Poll Enable
Parallel Poll Unconfigure
Selected Device Clear
Serial Poll Disable
Serial Poll Enable
Take Control
Unlisten
Untalk
† This multiline interface message is a proposed extension to the IEEE 488.1 specification to support the HS488 high-speed protocol.
GPIB for VXIpc Controllers and VxWorks A-4 © National Instruments Corporation
B
Status Word Conditions
This appendix describes the conditions reported in the status word, ibsta .
For information about how to use ibsta in your application program, refer
to Chapter 2, Developing Your Application with the VxWorks Drivers .
CIC
ATN
TACS
LACS
DTAS
DCAS
Mnemonic
ERR
TIMO
END
SRQI
CMPL
LOK
REM
Table B-1 shows the status word layout.
Bit Pos.
15
14
8
7
6
13
12
5
4
3
2
1
0
Table B-1. Status Word Layout
20
10
8
4
2
1
Hex
Value
8000
4000
2000
1000
100
80
40
Description
GPIB error
Time limit exceeded
END or EOS detected
SRQ interrupt received
I/O completed
Lockout State
Remote State
Controller-In-Charge
Attention is asserted
Talker
Listener
Device Trigger State
Device Clear State
© National Instruments Corporation B-1 GPIB for VXIpc Controllers and VxWorks
Appendix B Status Word Conditions
ERR
ERR is set in the status word following any call that results in an error. You can determine the particular error by examining the error variable iberr .
Appendix C, Error Codes and Solutions
, describes error codes that are recorded in iberr along with possible solutions. ERR is cleared following any call that does not result in an error.
TIMO
TIMO indicates that the timeout period has been exceeded. TIMO is set in the status word following an ibwait call if the TIMO bit of the mask parameter is set and the time limit expires. TIMO is also set following any
I/O functions (for example, ibcmd , ibrd , and ibwrt ) if a timeout occurs during one of these calls. TIMO is cleared in all other circumstances.
END
END indicates either that the GPIB EOI line has been asserted or, if you configure the software to terminate a read on an EOS byte, that the EOS byte has been received. If the GPIB board is performing a shadow handshake as a result of the ibgts function, any other function can return a status word with the END bit set if the END condition occurs before or during that call. END is cleared when any I/O operation is initiated.
SRQI
SRQI indicates that a GPIB device is requesting service. SRQI is set whenever the GPIB board is CIC and the GPIB SRQ line is asserted. SRQI is cleared either when the GPIB board ceases to be the CIC or when the
GPIB SRQ line is unasserted.
CMPL
CMPL indicates the condition of I/O operations. Because I/O calls in the
NI-488 driver are all synchronous (meaning the call does not return until the operation is complete), CMPL is always set.
GPIB for VXIpc Controllers and VxWorks B-2 © National Instruments Corporation
LOK
REM
CIC
ATN
Appendix B Status Word Conditions
LOK indicates whether the board is in a lockout state. While LOK is set, the ibloc function is inoperative for that board. LOK is set whenever the
GPIB board detects that the Local Lockout (LLO) message has been sent either by the GPIB board or by another Controller. LOK is cleared when the
System Controller unasserts the Remote Enable (REN) GPIB line.
REM indicates whether the board is in the remote state. REM is set whenever the Remote Enable (REN) GPIB line is asserted and the GPIB board detects that its listen address has been sent either by the GPIB board or by another Controller. REM is cleared in the following situations:
• When REN becomes unasserted
• When the GPIB board as a Listener detects that the Go to Local (GTL) command has been sent either by the GPIB board or by another
Controller
• When you call the ibloc function while the LOK bit is cleared in the status word
CIC indicates whether the GPIB board is the Controller-In-Charge. CIC is set either when you execute the ibsic function while the GPIB board is
System Controller or when another Controller passes control to the GPIB board. CIC is cleared either when the GPIB board detects Interface Clear
(IFC) from the System Controller or when the GPIB board passes control to another device.
ATN indicates the state of the GPIB Attention (ATN) line. ATN is set whenever the GPIB ATN line is asserted, and it is cleared when the ATN line is unasserted.
© National Instruments Corporation B-3 GPIB for VXIpc Controllers and VxWorks
Appendix B Status Word Conditions
TACS
TACS indicates whether the GPIB board is addressed as a Talker. TACS is set whenever the GPIB board detects that its talk address (and secondary address, if enabled) has been sent either by the GPIB board itself or by another Controller. TACS is cleared whenever the GPIB board detects the
Untalk (UNT) command, its own listen address, a talk address other than its own talk address, or Interface Clear (IFC).
LACS
LACS indicates whether the GPIB board is addressed as a Listener.
LACS is set whenever the GPIB board detects that its listen address
(and secondary address, if enabled) has been sent either by the GPIB board itself or by another Controller. LACS is also set whenever the GPIB board shadow handshakes as a result of the ibgts function. LACS is cleared whenever the GPIB board detects the Unlisten (UNL) command, its own talk address, Interface Clear (IFC), or that the ibgts function has been called without shadow handshake.
DTAS
DTAS indicates whether the GPIB board has detected a device trigger command. DTAS is set whenever the GPIB board, as a Listener, detects that the Group Execute Trigger (GET) command has been sent by another
Controller. DTAS is cleared on any call immediately following an ibwait call, if the DTAS bit is set in the ibwait mask parameter.
DCAS
DCAS indicates whether the GPIB board has detected a device clear command. DCAS is set whenever the GPIB board detects that the Device
Clear (DCL) command has been sent by another Controller, or whenever the GPIB board as a Listener detects that the Selected Device Clear (SDC) command has been sent by another Controller.
If you use the ibwait function to wait for DCAS and the wait is completed,
DCAS is cleared from ibsta after the next GPIB call. The same is true of reads and writes. If you call a read or write function such as ibwrt , and
DCAS is set in ibsta , the I/O operation is aborted. DCAS is cleared from ibsta after the next GPIB call.
GPIB for VXIpc Controllers and VxWorks B-4 © National Instruments Corporation
C
Error Codes and Solutions
This appendix describes each error, including conditions under which it might occur and possible solutions.
Error
Mnemonic
EDVR
ECIC
ENOL
EADR
EARG
ESAC
EABO
ENEB
ECAP
Table C-1 lists the GPIB error codes.
Table C-1. GPIB Error Codes
5
6
7
11
2
3
4 iberr
Value
0
1
Meaning
System error
Function requires GPIB board to be CIC
No Listeners on the GPIB
GPIB board not addressed correctly
Invalid argument to function call
GPIB board not System Controller as required
I/O operation aborted (timeout)
Nonexistent GPIB board
No capability for operation
© National Instruments Corporation C-1 GPIB for VXIpc Controllers and VxWorks
Appendix C Error Codes and Solutions
EDVR (0)
EDVR is returned when the board name passed to ibfind cannot be accessed. The global variable ibcntl contains an error code. This error occurs when you try to access a board that is not installed or configured properly.
EDVR is also returned if an invalid unit descriptor is passed to any NI-488 function call.
Solutions
Following are some possible solutions:
• Use only board names configured in the driver source code as parameters to the ibfind function.
• Use the unit descriptor returned from ibfind as the first parameter in subsequent NI-488 functions. Examine the variable before the failing function to make sure its value has not been corrupted.
ECIC (1)
ECIC is returned when one of the following board functions or routines is called while the board is not CIC:
• Any board-level NI-488 functions that issue GPIB command bytes: ibcmd , ibln , and ibrpp
• ibcac and ibgts
Solutions
Following are some possible solutions:
• Use ibsic to make the GPIB board become CIC on the GPIB.
• Use ibrsc 1 to make sure your GPIB board is configured as System
Controller.
• In multiple CIC situations, always be certain that the CIC bit appears in the status word ibsta before attempting these calls. If it does not appear, you can perform an ibwait (for CIC) call to delay further processing until control is passed to the board.
GPIB for VXIpc Controllers and VxWorks C-2 © National Instruments Corporation
Appendix C Error Codes and Solutions
ENOL (2)
Solutions
EADR (3)
Solutions
ENOL usually occurs when you attempt a write operation without addressing Listeners. ENOL can also indicate that the GPIB address the application uses for a device does not match the GPIB address of any device connected to the bus, that the GPIB cable is not connected to the device, or that the device is not powered on.
ENOL can occur in situations where the GPIB board is not the CIC and the
Controller asserts ATN before the write call in progress has ended.
Following are some possible solutions:
• Make sure that the GPIB address you are using matches the GPIB address of the device to which you want to write data.
• Use the appropriate hex code in ibcmd to address your device.
• Check your cable connections and make sure at least two-thirds of your devices are powered on.
• Reduce the write byte count to that which is expected by the Controller.
EADR occurs when the GPIB board is CIC and is not properly addressing itself before read and write functions.
EADR is also returned by the function ibgts when the shadow-handshake feature is requested and the GPIB ATN line is already unasserted. In this case, the shadow handshake is not possible and the error is returned to notify you of that fact.
Following are some possible solutions:
• Make sure that the GPIB board is addressed correctly using ibcmd before calling ibrd or ibwrt .
• Avoid calling ibgts except immediately after an ibcmd call.
( ibcmd causes ATN to be asserted.)
© National Instruments Corporation C-3 GPIB for VXIpc Controllers and VxWorks
Appendix C Error Codes and Solutions
EARG (4)
EARG results when an invalid argument is passed to a function call. The following are some examples:
• ibtmo called with a value not in the range 0 through 17
• ibeos called with meaningless bits set in the high byte of the second parameter
• ibpad or ibsad called with invalid addresses
• ibppc called with invalid parallel poll configurations
Solution
Make sure that the parameters passed to the NI-488 function are valid.
ESAC (5)
ESAC results when ibsic or ibsre is called when the GPIB board does not have System Controller capability.
Solution
Give the GPIB board System Controller capability by calling ibrsc 1 .
EABO (6)
EABO indicates that an I/O operation has been canceled, usually due to a timeout condition. Another cause is receiving the Device Clear message from the CIC while performing an I/O operation. Frequently, the I/O is not progressing (the Listener is not continuing to handshake or the Talker has stopped talking), or the byte count in the call which timed out was more than the other device was expecting.
Solutions
Following are some possible solutions:
• Use the correct byte count in input functions or have the Talker use the
END message to signify the end of the transfer.
• Lengthen the timeout period for the I/O operation using ibtmo .
• Make sure that you have configured your device to send data before you request data.
GPIB for VXIpc Controllers and VxWorks C-4 © National Instruments Corporation
Appendix C Error Codes and Solutions
ENEB (7)
Solution
ECAP (11)
ENEB occurs when no GPIB board exists at the I/O address specified when the driver is installed. This problem happens when the board is not physically plugged into the system, the I/O address specified during configuration does not match the actual board setting, or there is a system conflict with the base I/O address.
Make sure there is a GPIB board in your computer that is properly configured both in hardware and software using a valid base I/O address.
Solution
ECAP results when your GPIB board lacks the ability to carry out an operation or when a particular capability has been disabled in the software and a call is made that requires the capability.
Check the validity of the call, or make sure your GPIB interface board and the driver both have the needed capability.
© National Instruments Corporation C-5 GPIB for VXIpc Controllers and VxWorks
D
Customer Communication
For your convenience, this appendix contains forms to help you gather the information necessary to help us solve your technical problems and a form you can use to comment on the product documentation. When you contact us, we need the information on the Technical Support Form and the configuration form, if your manual contains one, about your system configuration to answer your questions as quickly as possible.
National Instruments has technical assistance through electronic, fax, and telephone systems to quickly provide the information you need. Our electronic services include a bulletin board service, an FTP site, a fax-on-demand system, and e-mail support. If you have a hardware or software problem, first try the electronic support systems. If the information available on these systems does not answer your questions, we offer fax and telephone support through our technical support centers, which are staffed by applications engineers.
Electronic Services
Bulletin Board Support
National Instruments has BBS and FTP sites dedicated for 24-hour support with a collection of files and documents to answer most common customer questions. From these sites, you can also download the latest instrument drivers, updates, and example programs. For recorded instructions on how to use the bulletin board and FTP services and for BBS automated information, call 512 795 6990. You can access these services at:
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FTP Support
To access our FTP site, log on to our Internet host, ftp.natinst.com
, as anonymous and use your Internet address, such as [email protected]
, as your password. The support files and documents are located in the /support directories.
© National Instruments Corporation D-1 GPIB for VXIpc Controllers and VxWorks
Fax-on-Demand Support
Fax-on-Demand is a 24-hour information retrieval system containing a library of documents on a wide range of technical information. You can access Fax-on-Demand from a touch-tone telephone at
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E-Mail Support (Currently USA Only)
You can submit technical support questions to the applications engineering team through e-mail at the
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National Instruments has branch offices all over the world. Use the list below to find the technical support number for your country. If there is no National Instruments office in your country, contact the source from which you purchased your software to obtain support.
Country
Australia
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Canada (Quebec)
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Korea
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Telephone
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02 757 00 20
011 288 3336
905 785 0085
514 694 8521
45 76 26 00
09 725 725 11
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089 741 31 30
2645 3186
03 6120092
02 413091
03 5472 2970
02 596 7456
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0348 433466
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2265886
91 640 0085
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01635 523545
512 795 8248
Fax
03 9879 6277
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02 757 03 11
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514 694 4399
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089 714 60 35
2686 8505
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02 41309215
03 5472 2977
02 596 7455
5 520 3282
0348 430673
32 84 86 00
2265887
91 640 0533
08 730 43 70
056 200 51 55
02 737 4644
01635 523154
512 794 5678
GPIB for VXIpc Controllers and VxWorks D-2 © National Instruments Corporation
Technical Support Form
Photocopy this form and update it each time you make changes to your software or hardware, and use the completed copy of this form as a reference for your current configuration. Completing this form accurately before contacting National Instruments for technical support helps our applications engineers answer your questions more efficiently.
If you are using any National Instruments hardware or software products related to this problem, include the configuration forms from their user manuals. Include additional pages if necessary.
Name __________________________________________________________________________
Company _______________________________________________________________________
Address ________________________________________________________________________
_______________________________________________________________________________
Fax ( ___ ) ________________Phone ( ___ ) __________________________________________
Computer brand____________ Model ___________________ Processor _____________________
Operating system (include version number) ____________________________________________
Clock speed ______MHz RAM _____MB Display adapter __________________________
Mouse ___yes ___no Other adapters installed _______________________________________
Hard disk capacity _____ MB Brand_________________________________________________
Instruments used _________________________________________________________________
_______________________________________________________________________________
National Instruments hardware product model _____________ Revision ____________________
Configuration ___________________________________________________________________
National Instruments software product ___________________ Version _____________________
Configuration ___________________________________________________________________
The problem is: __________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
List any error messages: ___________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
The following steps reproduce the problem: ___________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
Hardware and Software Configuration Form
Record the settings and revisions of your hardware and software on the line to the right of each item.
Complete a new copy of this form each time you revise your software or hardware configuration, and use this form as a reference for your current configuration. Completing this form accurately before contacting National Instruments for technical support helps our applications engineers answer your questions more efficiently.
National Instruments Products
GPIB hardware revision ___________________________________________________________
GIPB hardware settings (slot number, and so on) _______________________________________
NI-488 version___________________________________________________________________
Other Products
Computer make and model ________________________________________________________
Microprocessor __________________________________________________________________
Clock frequency or speed __________________________________________________________
Type of video board installed _______________________________________________________
Operating system version __________________________________________________________
Operating system mode ___________________________________________________________
Programming language ___________________________________________________________
Programming language version _____________________________________________________
Other boards in system ____________________________________________________________
Base I/O address of other boards ____________________________________________________
DMA channels of other boards _____________________________________________________
Interrupt level of other boards ______________________________________________________
Documentation Comment Form
National Instruments encourages you to comment on the documentation supplied with our products.
This information helps us provide quality products to meet your needs.
Title:
GPIB Reference Manual for VXIpc Embedded Controllers and VxWorks
Edition Date:
December 1997
Part Number:
321858A-01
Please comment on the completeness, clarity, and organization of the manual.
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If you find errors in the manual, please record the page numbers and describe the errors.
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Thank you for your help.
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512 794 5678
Glossary
Prefix n-
µmk-
M-
Meanings nanomicromillikilomega-
Value
10 –9
10 – 6
10 –3
10 3
10 6
A
acceptor handshake access board
ANSI
API
ASCII asynchronous
Listeners use this GPIB interface function to receive data, and all devices use it to receive commands. See handshake.
The GPIB board that controls and communicates with the devices on the bus that are attached to it.
American National Standards Institute.
Application programming interface.
American Standard Code for Information Interchange.
An action or event that occurs at an unpredictable time with respect to the execution of a program.
B
base I/O address board-level function
C
caller
See I/O address.
A rudimentary function that performs a single operation.
A place in the program from which a call is made; the calling function.
© National Instruments Corporation G-1 GPIB for VXIpc Controllers and VxWorks
Glossary
CFE
CFGn
CIC
Configuration Enable. The GPIB command which precedes CFGn and is used to place devices into their configuration mode.
These GPIB commands (CFG1 through CFG15) follow CFE and are used to configure all devices for the number of meters of cable in the system so that HS488 transfers occur without errors.
Controller-In-Charge. The device that manages the GPIB by sending interface messages to other devices.
Central processing unit.
CPU
D
DAV
DCL
DIO1 through DIO8
DMA driver
Data Valid. One of the three GPIB handshake lines. See handshake.
Device Clear. The GPIB command used to reset the device or internal functions of all devices. See SDC.
The GPIB lines that are used to transmit command or data bytes from one device to another.
Direct memory access. High-speed data transfer between the GPIB board and memory that is not handled directly by the CPU. Not available on some systems.
Device driver software installed within the operating system.
E
END or END Message A message that signals the end of a data string. END is sent by asserting the
GPIB End or Identify (EOI) line with the last data byte.
EOI A GPIB line that is used to signal either the last byte of a data message
(END) or the parallel poll Identify (IDY) message.
EOS or EOS Byte A 7- or 8-bit end-of-string character that is sent as the last byte of a data message.
End of transmission.
EOT
ESB The Event Status bit is part of the IEEE 488.2-defined status byte which is received from a device responding to a serial poll.
GPIB for VXIpc Controllers and VxWorks G-2 © National Instruments Corporation
Glossary
F
Function Return
G
GET
GPIB
GPIB address
GPIB board
GTL
H
handshake
Describes the return value of the function.
Group Execute Trigger. It is the GPIB command used to trigger a device or internal function of an addressed Listener.
General Purpose Interface Bus is the common name for the communications interface system defined in ANSI/IEEE Standard
488.1-1987, IEEE Standard Digital Interface for Programmable
Instrumentation, and ANSI/IEEE Standard 488.2-1992, IEEE Standard
Codes, Formats, Protocols, and Common Commands.
The address of a device on the GPIB, composed of a primary address
(MLA and MTA) and perhaps a secondary address (MSA). The GPIB board has both a GPIB address and an I/O address.
Refers to the National Instruments family of GPIB interface boards.
Go To Local. It is the GPIB command used to place an addressed Listener in local (front panel) control mode.
hex
The mechanism used to transfer bytes from the Source Handshake function of one device to the Acceptor Handshake function of another device. The three GPIB lines DAV, NRFD, and NDAC are used in an interlocked fashion to signal the phases of the transfer, so that bytes can be sent asynchronously (for example, without a clock) at the speed of the slowest device.
For more information about handshaking, refer to the ANSI/IEEE Standard
488.1-1987.
Hexadecimal; a number represented in base 16. For example, decimal 16 = hex 10.
© National Instruments Corporation G-3 GPIB for VXIpc Controllers and VxWorks
Glossary
I
ibcnt iberr ibsta
IEEE interface message
I/O
I/O address ist
After each NI-488 I/O function, this global variable contains the actual number of bytes transmitted.
A global variable that contains the specific error code associated with a function call that failed.
At the end of each function call, this global variable (status word) contains status information.
Institute of Electrical and Electronic Engineers.
A broadcast message sent from the Controller to all devices and used to manage the GPIB. Interface messages are also referred to as GPIB commands.
Input/Output. In the context of this manual, the transmission of commands or messages between the computer via the GPIB board and other devices on the GPIB.
The address of the GPIB board from the point of view of the CPU, as opposed to the GPIB address of the GPIB board. Also called port address or board address.
An Individual Status bit of the status byte used in the Parallel Poll
Configure function.
K
kernel kernel-level implementation
The set of programs in an operating system that implements basic system functions.
The linking or installation of the NI-488 driver into the operating system kernel so that the driver functions as a general system resource available to all application programs.
L
language interface Code that enables an application program that uses NI-488 functions to access the driver.
GPIB for VXIpc Controllers and VxWorks G-4 © National Instruments Corporation
M
m
MAV
MLA
MSA
Listener
LLO
Glossary
A GPIB device that receives data messages from a Talker.
Local Lockout. The GPIB command used to tell all devices that they may or should ignore remote (GPIB) data messages or local (front panel) controls, depending on whether the device is in local or remote program mode.
Meters.
The Message Available bit is part of the IEEE 488.2-defined status byte which is received from a device responding to a serial poll.
My Listen Address. A GPIB command used to address a device to be a
Listener. It can be any one of the 31 primary addresses.
My Secondary Address. The GPIB command used to address a device to be a Listener or a Talker when extended (two byte) addressing is used. The complete address is a MLA or MTA address followed by an MSA address.
There are 31 secondary addresses for a total of 961 distinct listen or talk addresses for devices.
My Talk Address. A GPIB command used to address a device to be a
Talker. It can be any one of the 31 primary addresses.
MTA
N
NDAC
NRFD
O
OS
P
parallel poll
Not Data Accepted. One of the three GPIB handshake lines. See handshake.
Not Ready For Data. One of the three GPIB handshake lines.
See handshake.
Operating system.
The process of polling all configured devices at once and reading a composite poll response. See serial poll.
© National Instruments Corporation G-5 GPIB for VXIpc Controllers and VxWorks
Glossary
PPC
PPD
PPE
PPU
S
s
SDC serial poll service request
SPD
SPE
SRQ status byte status word synchronous
Parallel Poll Configure. It is the GPIB command used to configure an addressed Listener to participate in polls.
Parallel Poll Disable. It is the GPIB command used to disable a configured device from participating in polls. There are 16 PPD commands.
Parallel Poll Enable. It is the GPIB command used to enable a configured device to participate in polls and to assign a DIO response line. There are
16 PPE commands.
Parallel Poll Unconfigure. It is the GPIB command used to disable any device from participating in polls.
Seconds.
Selected Device Clear. The GPIB command used to reset internal or device functions of an addressed Listener. See DCL.
The process of polling and reading the status byte of one device at a time.
See parallel poll.
See SRQ.
Serial Poll Disable. The GPIB command used to cancel an SPE command.
Serial Poll Enable. The GPIB command used to enable a specific device to be polled. That device must also be addressed to talk. See SPD.
Service Request. The GPIB line that a device asserts to notify the CIC that the device needs servicing.
The IEEE 488.2-defined data byte sent by a device when it is serially polled.
See ibsta .
Refers to the relationship between the NI-488 driver functions and a process when executing driver functions is predictable; the process is blocked until the driver completes the function.
GPIB for VXIpc Controllers and VxWorks G-6 © National Instruments Corporation
System Controller
Glossary
The single designated Controller that can assert control (become CIC of the
GPIB) by sending the Interface Clear (IFC) message. Other devices can become CIC only by having control passed to them.
T
Talker
TCT timeout
A GPIB device that sends data messages to Listeners.
Take Control. The GPIB command used to pass control of the bus from the current Controller to an addressed Talker.
A feature of the NI-488 driver that prevents I/O functions from hanging indefinitely when there is a problem on the GPIB.
U
ud
UNL
UNT user-level implementation
Unit descriptor. A variable name and first argument of each function call that contains the unit descriptor of the GPIB interface board or other GPIB device that is the object of the function.
Unlisten. The GPIB command used to unaddress any active Listeners.
Untalk. The GPIB command used to unaddress an active Talker.
The static or dynamic linking of the NI-488 driver directly to a user application program. This implementation method is not available on some operating systems, for which a kernel-level implementation is the only option.
© National Instruments Corporation G-7 GPIB for VXIpc Controllers and VxWorks
Index
A
active Controller, 1-1 address functions
IBPAD, 3-17
IBSAD, 3-27 addresses. See GPIB addresses.
ANSI/IEEE Standard 488.1-1987, 1-1
ANSI/IEEE Standard 488.2-1992, 1-1 application development. See also GPIB programming techniques.
compiling and linking, 2-5 to 2-6 debugging, 2-6 to 2-8 communication errors, 2-7 configuration errors, 2-6 timing errors, 2-7 using global status variables, 2-6 global variables for checking status,
2-3 to 2-5 count variables - ibcnt and ibcntl, 2-5 error variable - iberr, 2-4 status word - ibsta, 2-3 to 2-4
GPIB library files provided with VxWorks,
2-2 to 2-3 items to include for C applications,
2-2 to 2-3
NI-488 functions, 2-2
VxWorks NI-488 and ESP-488 drivers,
2-1 to 2-2
ATN (attention) line (table), 1-3
ATN status word condition, B-3
B
bulletin board support, D-1
C
CIC. See Controller-in-Charge (CIC).
CIC status word condition, B-3 clear functions
IBIST, 3-11
IBSIC, 3-24
IBSRE, 3-25
CMPL status word condition, B-2 command function (IBCMD), 3-5 communication errors repeat addressing, 2-7 termination method, 2-7 compiling and linking applications, 2-5 to 2-6 configuration, 1-4 to 1-5 controlling more than one board, 1-4 to 1-5 linear and star system configuration
(illustration), 1-4 requirements, 1-5 configuration errors, debugging, 2-6 control line status. See IBLINES function.
controller functions
IBCAC, 3-4
IBGTS, 3-10
IBRSC, 3-21
Controller-in-Charge (CIC) active Controller as CIC, 1-1
System Controller as, 1-1
Controllers definition, 1-1 idle Controller, 1-1
System Controller, 1-1 count variables (ibcnt and ibcntl), 2-5 customer communication, xi, D-1 to D-2
© National Instruments Corporation I-1 GPIB for VXIpc Controllers and VxWorks
Index
D
data lines, 1-2 data transfers terminating
GPIB programming technique,
4-1 to 4-2
DAV (data valid) line (table), 1-3
DCAS status word condition, B-4 debugging communication errors, 2-7 repeat addressing, 2-7 termination method, 2-7 configuration errors, 2-6 global status variables, 2-6 timing errors, 2-7 developing applications. See application development.
documentation conventions used in manual, x organization of manual, ix related documentation, x drivers
ESP-488 driver, 2-1 to 2-2
NI-488 driver, 2-1 to 2-2
DTAS status word condition, B-4
E
EABO error code, C-4
EADR error code, C-3
EARG error code, C-4
ECAP error code, C-5
ECIC error code, C-2
EDVR error code, C-2 electronic support services, D-1 to D-2 e-mail support, D-2
END status word condition, B-2 end-of-string. See EOS.
ENEB error code, C-5
GPIB for VXIpc Controllers and VxWorks I-2
ENOL error code, C-3
EOI (end or identify) line enabling or disabling. See IBEOT function.
purpose (table), 1-3
EOS comparison method, 4-1
EOS configurations (table), 3-6
EOS read method, 4-1
EOS write method, 4-1
ERR status word condition, B-2 error codes and solutions, C-1 to C-5
EABO, C-4
EADR, C-3
EARG, C-4
ECAP, C-5
ECIC, C-2
EDVR, C-2
ENEB, C-5
ENOL, C-3
ESAC, C-4 error variable - iberr, 2-4
ESAC error code, C-4
ESP-488 driver, 2-1 to 2-2
F
fax and telephone support numbers, D-2
Fax-on-Demand support, D-2
FTP support, D-1 functions. See NI-488 functions.
G
General Purpose Interface Bus. See GPIB.
global variables, 2-3 to 2-5 count variables - ibcnt and ibcntl, 2-5 debugging applications, 2-6 error variable - iberr, 2-4 status word - ibsta, 2-3 to 2-4, B-1 to B-4
© National Instruments Corporation
GPIB configuration, 1-4 to 1-5 controlling more than one board,
1-4 to 1-5 linear and star system configuration
(illustration), 1-4 requirements, 1-5 definition, 1-1 overview, 1-1 sending messages across, 1-2 to 1-3 data lines, 1-2 handshake lines, 1-3 interface management lines, 1-3
Talkers, Listeners, and Controllers, 1-1
GPIB addresses address bits (figure), 1-2 listen address, 1-2 primary, 1-2 purpose, 1-2 secondary, 1-2 talk address, 1-2
GPIB programming techniques. See also application development.
parallel polling, 4-4 to 4-5 serial polling, 4-2 to 4-4 service requests from IEEE 488 devices, 4-3 from IEEE 488.2 devices, 4-3
SRQ and serial polling with NI-488 device functions,
4-3 to 4-4 with NI-488.2 routines, 4-4
Talker/Listener applications, 4-2 termination of data transfers, 4-1 to 4-2 waiting for GPIB conditions, 4-2
H
handshake lines, 1-3
I
IBCAC function, 3-4
IBCMD function, 3-5 ibcnt and ibcntl variables, 2-5
IBEOS function description, 3-6 to 3-7
EOS configurations (table), 3-6 examples, 3-6 terminating data transfers, 4-1
IBEOT function description, 3-8 terminating data transfer, 4-1 iberr (error variable), 2-4 to 2-5
IBFIND function, 3-9
IBGTS function, 3-10
IBIST function, 3-11
IBLINES function, 3-12 to 3-13
IBLN function, 3-14
IBLOC function, 3-15
IBONL function, 3-16
IBPAD function, 3-17
IBPPC function, 3-18
IBRD function, 3-19
IBRPP function, 3-20
IBRSC function, 3-21
IBRSV function, 3-22
IBSAD function, 3-27
IBSIC function, 3-24
IBSRE function, 3-25 ibsta. See status word - ibsta.
IBTMO function, 3-26 to 3-27
IBWAIT function description, 3-28 to 3-29 programming techniques, 4-2
IBWRT function, 3-30
IEEE Standard 488.1-1987. See GPIB.
IFC (interface clear) line (table), 1-3 interface clear function (IBSIC), 3-24 interface management lines (table), 1-3
Index
© National Instruments Corporation I-3 GPIB for VXIpc Controllers and VxWorks
Index
L
LACS status word condition, B-4 linking and compiling applications, 2-5 to 2-6 listen address, setting, 1-2
Listeners definition, 1-1 finding using IBLN function, 3-14
Talker/Listener applications, 4-2 local function (IBLOC), 3-15
LOK status word condition, B-3
M
manual. See documentation.
messages, sending across GPIB, 1-2 to 1-3 data lines, 1-2 handshake lines, 1-3 interface management lines, 1-3 multiline interface messages, A-1 to A-4
N
NDAC (not data accepted) line (table), 1-3
NI-488 driver developing applications with, 2-1 to 2-2
GPIB library files provided with
VxWorks, 2-1 to 2-2
NI-488 functions alphabetical list of functions (table),
3-2 to 3-3 developing applications, 2-2
IBCAC, 3-4
IBCMD, 3-5
IBEOS, 3-6 to 3-7
IBEOT, 3-8
IBFIND, 3-9
IBGTS, 3-10
IBIST, 3-11
IBLINES, 3-12 to 3-13
IBLN, 3-14
IBLOC, 3-15
GPIB for VXIpc Controllers and VxWorks I-4
IBONL, 3-16
IBPAD, 3-17
IBPPC, 3-18
IBRD, 3-19
IBRPP, 3-20
IBRSC, 3-21
IBRSV, 3-22
IBSAD, 3-27
IBSIC, 3-24
IBSRE, 3-25
IBTMO, 3-26 to 3-27
IBWAIT, 3-28 to 3-29
IBWRT, 3-30
NRFD (not ready for data) line (table), 1-3
O
online/offline function. See IBONL function.
P
parallel polling, 4-4 to 4-5 parallel polling functions
IBIST, 3-11
IBPPC, 3-18
IBRPP, 3-20 primary GPIB address changing with IBPAD function, 3-17 definition, 1-2 programming. See application development;
GPIB programming techniques.
R
read function (IBRD), 3-19
REM status word condition, B-3 remote function (IBSRE), 3-25
REN (remote enable) line (table), 1-3 repeat addressing, 2-7
© National Instruments Corporation
S
secondary GPIB address, 1-2 serial polling, 4-2 to 4-4 service requests from IEEE 488 devices, 4-3 from IEEE 488.2 devices, 4-3
SRQ and serial polling with NI-488 device functions,
4-3 to 4-4 with NI-488.2 routines, 4-4 using IBRSV function, 3-22 setting up your system. See configuration.
SRQ (service request) line purpose (table), 1-3 serial polling, 4-3
SRQI status word condition, B-2 status word - ibsta
ATN, B-3
CIC, B-3
CMPL, B-2
DCAS, B-4
DTAS, B-4
END, B-2
ERR, B-2
LACS, B-4
LOK, B-3
REM, B-3
SRQI, B-2
Index status word layout (table), 2-3 to 2-4, B-1
TACS, B-4
TIMO, B-2 using in applications, 2-3 to 2-4 debugging, 2-6
System Controller, 1-1
T
TACS status word condition, B-4 talk address, setting, 1-2
Talkers definition, 1-1
Talker/Listener applications, 4-2 technical support, D-1 to D-2 telephone and fax support numbers, D-2 termination of data transfers methods for, 4-1 to 4-2 problems in applications, 2-7 timeout code values (table), 3-26 to 3-27 timing errors, debugging, 2-6
TIMO status word condition, B-2
W
wait function (IBWAIT), 3-28 to 3-29 wait mask layout (table), 3-28 to 3-29 write function (IBWRT), 3-30
© National Instruments Corporation I-5 GPIB for VXIpc Controllers and VxWorks
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