For more than two decades, scientists and engineers have used the IEEE488 and the universal interface bus GPIB extensively in automated instrument systems. When popular computer technology enters the field of test and measurement, and when bus technologies such as USB, Ethernet, and IEEE1394 are applied to connect instruments, whether or not the GPIB interface can become the first choice for instrument control bus interface becomes a problem. GPIB will continue to exist for many years to come as GPIB has a powerful function and a broad user base. However, the instrument control industry will likely begin to enter the world of mixed I/O systems. This paper discusses the future development of the instrumentation system when GPIB is used in combination with other buses, and the importance of software "upward compatibility" in instrument control.
GPIB basics
GPIB is designed for instrument control applications. In the 1970s, the birth of the IEEE488 standard led to GPIB's electrical, mechanical, and functional specifications in 1975; in 1987, the ANSI/IEEE standard 488.2 more clearly defined the way in which controllers and instruments communicate through GPIB. The previous specification is more complete. GPIB is a digital 8-bit parallel communication interface with a transmission rate of 8 Mbyte/s. A controller provided by the bus can connect up to 14 instruments within 20 meters of the cable length. However, users can overcome these two limitations by using GPIB amplifiers and extenders. GPIB cables and connectors are products that are versatile and meet industry standards and can be used in any environment.
The advantages of new bus technology
In the past, computers only included serial ports (RS-232) and parallel ports. In recent years, computers have provided Ethernet, USB (Universal Serial Bus), and sometimes even IEEE1394 (FireWire) interfaces. These new buses have many attractive features - easy to use (USB), easy to connect (Ethernet) and high speed (IEEE1394).
USB
The USB design is mainly used to connect peripheral devices such as keyboards, scanners, and disk drives. Apple Computer pioneered the use of USB as its sole serial port in 1998. In the past few years, the number of devices using the USB connection in the computer industry has greatly increased.
With the current USB 1.1 specification, the data transfer rate is as high as 1.5 Mbyte/s, while the next-generation USB products will use the USB 2.0 specification, which will increase the bus data transfer rate to 60 Mbyte/s. The USB2.0 specification is compatible with USB1.1 devices and can even use the same connector. Since the Universal Serial Bus is a plug-and-play technology, whenever a new device is added, the USB host automatically tests and recognizes its identity, and then adjusts its configuration appropriately, and an interface can control 127 devices at the same time. For the Windows operating system, the USB link can currently only be executed on Windows 2000/XP/98.
USB has the advantage of being inexpensive and easy to connect instruments and computers. In addition, USB provides more convenient serial port functions such as: hot swap, built-in operating system fine-tuning, high flexibility, etc., to improve the traditional serial port technology.
Although USB has many attractive advantages, there are also some drawbacks in instrument control. First of all, USB cables do not have industry standard specifications. In a noisy environment, data may be lost. In addition, the USB cable has no locking mechanism—the cable may be easily removed from the computer or the instrument. The length of the cable (including the use of an on-line repeater) can be up to 30 meters. Finally, there is no industrial transmission standard for USB in the instrument control and it needs to be designed by the instrument manufacturer.
Although USB has some disadvantages, due to the current widespread use on computers and the high speed of USB2.0, it has become the leading trend of instrument control in the future. Although few instruments currently provide USB control options, users can use bridges and USB to link their instrument-controlled applications. The bridge provides the user with a bridge between USB and GPIB. The bridge will be discussed later in this paper.
Ethernet
Recently, instrument manufacturers have begun to use the Ethernet network as another communication interface option for individual instruments. Although Ethernet is still a new application technology in instrument control, it has been widely used as a mature technology in other aspects of measurement systems. There are more than 100 million computers in the world that have Ethernet capabilities, making it an inevitable trend for the use of Ethernet as an instrument control.
The application of Ethernet-based instrument control can take advantage of the features of the bus technology, including instrument remote control, resource sharing within the enterprise, and convenient report generation. In addition, users can also make full use of the existing Ethernet network. However, this advantage may also be a problem for some companies, because it will force network administrators involved in traditional engineering applications.
For Ethernet networks to be used for instrument control, the following factors need to be considered: transmission rate, determinism, and security. The most common Ethernet network transmission rate is 10BaseT or 100BaseTX, respectively reaching transmission rates of 10Mb/s and 100Mb/s. However, these transmission rates are rarely achieved due to the traffic, fixed use, and insufficient data traffic of other networks. The uncertainty of the transmission rate determines that the communication on the Ethernet network cannot be confirmed. Finally, in the face of sensitive data users, there must be further security measures to ensure the integrity and privacy of the data.
IEEE1394 (FireWire)
The IEEE1394-1995 standard, also known as FireWire (registered trademark of Apple Computer), is an efficient serial bus developed by Apple Computer in the 1980s. At present, the data throughput rate of IEEE1394 is up to 50 Mbyte/s. However, the IEEE1394 trade association is amending its specifications and intends to increase the data transmission rate to 400 Mbyte/s. Since according to the 1394 specification, the bus connection of the device must be within 4.5 meters, the connection of 16 instruments will also be within 72 meters. In the Windows operating system, only Microsoft's Windows 2000/XP/98 is currently compatible with 1394.
The IEEE 1394 bus offers great potential for high-speed transmission applications. Many digital cameras and other consumer electronics products already include the IEEE 1394 interface for data transmission. The high bandwidth of IEEE1394 provides a viable solution for complex multimedia applications. The IEEE 1394 is more superior than the USB, and it has a transmission protocol defined on the bus technology specifically for controlling instruments. However, only a few instruments currently have a 1394 interface.
Although IEEE1394 has many advantages in instrument control, such as high bandwidth, there are still some factors that hinder its current development. The main drawback of IEEE1394 is that the 1394 interface is not built into the perimeter of Intel's PC integrated chips (all Macintosh computers have a built-in 1394 interface). Therefore, Intel's PC users must have an external 1394 controller, especially for PCI boards. Although the FireWire cable is lightweight and flexible, it does not meet the industry standard specifications, so data loss may occur in some test and measurement applications.
GPIB basics
GPIB is designed for instrument control applications. In the 1970s, the birth of the IEEE488 standard led to GPIB's electrical, mechanical, and functional specifications in 1975; in 1987, the ANSI/IEEE standard 488.2 more clearly defined the way in which controllers and instruments communicate through GPIB. The previous specification is more complete. GPIB is a digital 8-bit parallel communication interface with a transmission rate of 8 Mbyte/s. A controller provided by the bus can connect up to 14 instruments within 20 meters of the cable length. However, users can overcome these two limitations by using GPIB amplifiers and extenders. GPIB cables and connectors are products that are versatile and meet industry standards and can be used in any environment.
The advantages of new bus technology
In the past, computers only included serial ports (RS-232) and parallel ports. In recent years, computers have provided Ethernet, USB (Universal Serial Bus), and sometimes even IEEE1394 (FireWire) interfaces. These new buses have many attractive features - easy to use (USB), easy to connect (Ethernet) and high speed (IEEE1394).
USB
The USB design is mainly used to connect peripheral devices such as keyboards, scanners, and disk drives. Apple Computer pioneered the use of USB as its sole serial port in 1998. In the past few years, the number of devices using the USB connection in the computer industry has greatly increased.
With the current USB 1.1 specification, the data transfer rate is as high as 1.5 Mbyte/s, while the next-generation USB products will use the USB 2.0 specification, which will increase the bus data transfer rate to 60 Mbyte/s. The USB2.0 specification is compatible with USB1.1 devices and can even use the same connector. Since the Universal Serial Bus is a plug-and-play technology, whenever a new device is added, the USB host automatically tests and recognizes its identity, and then adjusts its configuration appropriately, and an interface can control 127 devices at the same time. For the Windows operating system, the USB link can currently only be executed on Windows 2000/XP/98.
USB has the advantage of being inexpensive and easy to connect instruments and computers. In addition, USB provides more convenient serial port functions such as: hot swap, built-in operating system fine-tuning, high flexibility, etc., to improve the traditional serial port technology.
Although USB has many attractive advantages, there are also some drawbacks in instrument control. First of all, USB cables do not have industry standard specifications. In a noisy environment, data may be lost. In addition, the USB cable has no locking mechanism—the cable may be easily removed from the computer or the instrument. The length of the cable (including the use of an on-line repeater) can be up to 30 meters. Finally, there is no industrial transmission standard for USB in the instrument control and it needs to be designed by the instrument manufacturer.
Although USB has some disadvantages, due to the current widespread use on computers and the high speed of USB2.0, it has become the leading trend of instrument control in the future. Although few instruments currently provide USB control options, users can use bridges and USB to link their instrument-controlled applications. The bridge provides the user with a bridge between USB and GPIB. The bridge will be discussed later in this paper.
Ethernet
Recently, instrument manufacturers have begun to use the Ethernet network as another communication interface option for individual instruments. Although Ethernet is still a new application technology in instrument control, it has been widely used as a mature technology in other aspects of measurement systems. There are more than 100 million computers in the world that have Ethernet capabilities, making it an inevitable trend for the use of Ethernet as an instrument control.
The application of Ethernet-based instrument control can take advantage of the features of the bus technology, including instrument remote control, resource sharing within the enterprise, and convenient report generation. In addition, users can also make full use of the existing Ethernet network. However, this advantage may also be a problem for some companies, because it will force network administrators involved in traditional engineering applications.
For Ethernet networks to be used for instrument control, the following factors need to be considered: transmission rate, determinism, and security. The most common Ethernet network transmission rate is 10BaseT or 100BaseTX, respectively reaching transmission rates of 10Mb/s and 100Mb/s. However, these transmission rates are rarely achieved due to the traffic, fixed use, and insufficient data traffic of other networks. The uncertainty of the transmission rate determines that the communication on the Ethernet network cannot be confirmed. Finally, in the face of sensitive data users, there must be further security measures to ensure the integrity and privacy of the data.
IEEE1394 (FireWire)
The IEEE1394-1995 standard, also known as FireWire (registered trademark of Apple Computer), is an efficient serial bus developed by Apple Computer in the 1980s. At present, the data throughput rate of IEEE1394 is up to 50 Mbyte/s. However, the IEEE1394 trade association is amending its specifications and intends to increase the data transmission rate to 400 Mbyte/s. Since according to the 1394 specification, the bus connection of the device must be within 4.5 meters, the connection of 16 instruments will also be within 72 meters. In the Windows operating system, only Microsoft's Windows 2000/XP/98 is currently compatible with 1394.
The IEEE 1394 bus offers great potential for high-speed transmission applications. Many digital cameras and other consumer electronics products already include the IEEE 1394 interface for data transmission. The high bandwidth of IEEE1394 provides a viable solution for complex multimedia applications. The IEEE 1394 is more superior than the USB, and it has a transmission protocol defined on the bus technology specifically for controlling instruments. However, only a few instruments currently have a 1394 interface.
Although IEEE1394 has many advantages in instrument control, such as high bandwidth, there are still some factors that hinder its current development. The main drawback of IEEE1394 is that the 1394 interface is not built into the perimeter of Intel's PC integrated chips (all Macintosh computers have a built-in 1394 interface). Therefore, Intel's PC users must have an external 1394 controller, especially for PCI boards. Although the FireWire cable is lightweight and flexible, it does not meet the industry standard specifications, so data loss may occur in some test and measurement applications.
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