An introduction of the IEC 625 (IEEE 488) standard interface

The IEC 625 interface system for programmable measuring instruments is introduced. The interface is a high speed asynchronous bit-parallel byte-serial communications link with handshaking and interface management and control. Instruments can be connected to the interface bus in a linear (daisychain) or star configuration or a mixture of the two, and can operate in a single master multislave arrangement. The interface is optimized for high speed communications between instruments in close proximity in electrically quiet surroundings. The maximum number of instruments that can be interconnected in a single system is 15. The total bus length must not exceed 20 m or the number of instruments x 2 m, whichever is shorter. The maximum communication rate is 1 Mbyte/sec. Dedicated LSI devices which implement the full interface or a subset of it are discussed. The implications of incorporating the interface in instrumentation are examined in terms of the product cost and complexity.