IEEE-488 - Standards

Standards

In 1975, the IEEE standardized the bus as Standard Digital Interface for Programmable Instrumentation, IEEE-488; it was revised in 1978 (producing IEEE-488-1978). The standard was revised in 1987, and redesignated as IEEE-488.1 (IEEE-488.1-1987). These standards formalized the mechanical, electrical, and basic protocol parameters of GPIB, but said nothing about the format of commands or data.

In 1987, IEEE introduced Standard Codes, Formats, Protocols, and Common Commands, IEEE-488.2. It was revised in 1992. IEEE-488.2 provided for basic syntax and format conventions, as well as device-independent commands, data structures, error protocols, and the like. IEEE-488.2 built on IEEE-488.1 without superseding it; equipment can conform to IEEE-488.1 without following IEEE-488.2.

While IEEE-488.1 defined the hardware and IEEE-488.2 defined the protocol, there was still no standard for instrument-specific commands. Commands to control the same class of instrument, e.g., multimeters, would vary between manufacturers and even models.

The United States Air Force, and later Hewlett-Packard, recognized this problem. In 1989, HP developed their TML language which was the forerunner to Standard Commands for Programmable Instrumentation (SCPI). SCPI was introduced as an industry standard in 1990. SCPI added standard generic commands, and a series of instrument classes with corresponding class-specific commands. SCPI mandated the IEEE-488.2 syntax, but allowed other (non-IEEE-488.1) physical transports.

The IEC developed their own standards in parallel with the IEEE, withIEC-60625-1 and IEC-60625-2, later replaced by IEC-60488.

National Instruments introduced a backward-compatible extension to IEEE-488.1, originally known as HS-488. It increased the maximum data rate to 8 Mbyte/s, although the rate decreases as more devices are connected to the bus. This was incorporated into the standard in 2003 (IEEE-488.1-2003), over HP's objections.

In 2004, the IEEE and IEC combined their respective standards into a "Dual Logo" IEEE/IEC standard IEC-60488-1, Standard for Higher Performance Protocol for the Standard Digital Interface for Programmable Instrumentation - Part 1: General, replaces IEEE-488.1/IEC-60625-1, and IEC-60488-2,Part 2: Codes, Formats, Protocols and Common Commands, replaces IEEE-488.2/IEC-60625-2.