GPIB Controllers and GPIB Interface Boards Information
GPIB controllers and GPIB interface boards are devices that enable communications between GPIB buses and GPIB networks. Originally developed by Hewlett Packard (HP), the GPIB or HPIB bus provides a standard interface for communication between instruments from different sources. GPIB controllers plug into GPIB buses and manage the flow of data between devices that send information (talkers) and devices that receive information (listeners). GPIB controllers send commands to all of the devices in the GPIB network and convert active talkers to active listeners as necessary. A minimum system consists of one GPIB controller and one talker or listener; however, the current GPIB standard allows up to 14 devices to be connected to a GPIB adaptor card. GPIB interface boards are used in systems that do not require GPIB controllers. In these configurations, talkers and listeners do not exchange functions. Each listen-only device requires a GPIB interface board.
GPIB controllers and GPIB interface boards meet standards defined by the Institute of Electrical and Electronics Engineers (IEEE) and other organizations. IEEE 488.1 defines mechanical, electrical and protocol specifications for interconnecting programmable instruments. It supports up to 14 devices and a maximum data transfer rate of 1 MBps. IEEE 488.2 is a superset of IEEE 488.1 that standardizes data formats, status reporting, error handling, and controller commands. High Speed 488 (HS488) is a newer standard that features data transfer rates up to 8 MBps using standard GPIB cables. At the hardware level, HS488 uses application specific integrated circuits (ASICs).
GPIB controllers and GPIB interface boards work with a variety of computer buses. Peripheral component interconnect (PCI) is a local bus system designed for high-end computer systems. Compact PCI (cPCI) is a high-performance bus that uses the electrical standards of the PCI bus in a rugged Eurocard. PCI extensions for instrumentation (PXI) is a superset of cPCI that adds timing and triggering functions. VersaModule Eurocard (VME) buses are available in both 32-bit (VME32) and 64-bit (VME66) versions. Often referred to as the “blue collar bus”, the simple-to-design or simple-to-debug (STD) bus is suitable for factory and industrial environments. Industry standard architecture (ISA) is a standard for buses that can handle 16-bit data transfers at clock speeds of 8 MHz. Extended ISA (EISA) also runs at 8 MHz, but is capable of 32-bit data transfers. Multibus features a modular architecture that is well-suited for a variety of embedded applications. Small computer system interface (SCSI) is a parallel interface for personal computers (PCs) and other devices. Other specialized and proprietary buses are also available.
GPIB controllers and GPIB interface boards vary in terms of specifications and features. Specifications include the number of ports and the maximum GPIB data transfer rate. Features include direct memory access; first in, first out buffering; and product certifications. Direct memory access (DMA), a method for speeding data transfers, sends data to the main memory without first passing it through the central processing unit (CPU). First in, first out (FIFO) buffers are used to store acquired data temporarily, until it can be transferred to system memory or another device. Buffering the data allows both a host bus and a GPIB bus to access data at the same time. In terms of product certification, some GPIB controllers and GPIB interface boards meet requirements established by the U.S. Federal Communication Commission (FCC). Others bear the CE Mark to indicate conformity with relevant European Union (EU) directives.