IEEE-488 / GPIB (General Purpose Interface Bus)

IEEE-488 General purpose interface bus and appropriate protocol are widely used in hardware-software systems for the connection of PC and work station with measurement instruments (e.g. in data acquisition systems). The protocol was developed in 60s in Hewlett-Packard and its initial name was HPIB (Hewlett-Packard Interace Bus). Afterwards other companies took up the initiative and started to use the protocol for their own purposes. In the middle of 70s the protocol was standardized by American Institute of Electrical and Electronics Engineers (IEEE) and then given another name – IEEE-488 (by number of the standard) or GRIB (General Purpose Interface Bus).

Since IEEE-488 bus is well standardized and tested; the majority of manufacturers of automated measuring systems and instruments build GRIB interfaces into their devices as the main data transfer channel.

Devices connected to IEEE-488 interfaces can have two conditions "listener" (read messages from the bus) or “talker” (send messages to the bus) or be in a condition of “controller”. In every certain moment only one device can stay in “talker” condition while the number of those in “listener” condition can reach any quantity. Controller can determine which devices stay in “talker” and “listener” conditions at the moment.

The bus consists of 24 wires (16 signal lines for data transfer: 8 straight and 8 return; 3 matching; 5 for the bus control) and configured in such a way that it can serve up to 15 clients with addresses from 0 till 30 inclusive (the devices addresses should be different).

GRIB interface cards exist for PCI, PC Card (PCMCA), ISA, NuBus, Sbus and NECBus.

GPIB (HS-488), so-called high-speed protocol, offered by National Instruments in 1996, allows increasing bus bandwidth up to 8 MB/s using standard cables and hardware base. For one operation “talker” is capable of sending as many data bytes as “listener” may accept, depending on the availability of free buffers. HS-488 protocol is fully compatible with existing systems based on IEEE-488.1, that is why devices of both types may co-exist on one bus.

One of the components of GPIB system of commands is Standard Commands for Programming Instruments (or SCPI) which was accepted in 1990. SCPI defines standard rules for the reduction of keywords used as commands.

Auxiliary information is taken from iXBT.com.