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Foreword 

(This Foreword is not a part of ANSI/IEEE Std 675-1982, IEEE Standard, Multiple Controllers in a CAMAC Crate.)

This standard makes provision for the use of auxiliary controllers in a CAMAC crate to extend the capabilities and ˝elds of application of the CAMAC modular instrumentation and interface system of ANSI/IEEE Std 583-1982, Modular Instrumentation and Digital Interface System (CAMAC). (Also Report EUR 4100e of the Commissions of the European Communities.) The report on which this document is based (Dept of Energy Report DOE/EV-007), was prepared by the NIM Committee of the United States Department of Energy* and the ESONE Committee of European Laboratories**. Corresponding documents are ESONE Report EUR 6500e and IEC Publication 729 of the International Electrotechnical Commission.

Auxiliary Controllers (ACs), located in several crates on a CAMAC Command Highway (Parallel Branch or Serial), can provide the user with an extremely effective distributed processing capability. This capability is useful in both data acquisition and automatic control systems where parallel processing is desirable. Auxiliary controllers can be of various degrees of sophistication, and some may include processor elements for increased autonomy from central computers.

A further extension of the AC-based CAMAC system may include a special communication channel direct from an AC to another element in the system. High-speed block transfer of data can be effected to and from the AC in such a case.

To permit use of the ACs in CAMAC crates, this report defines the hardware and protocol so as to:

1) Provide means for granting control of the Dataway to auxiliary controllers that request control and to provide a priority selection scheme to arbitrate in the case of simultaneous requests from multiple controllers.

2) Provide means for the auxiliary controller to address (a) the dedicated module address lines and (b) the dedicated interrupt request LAM (Look-at-Me) lines, all of which terminate only at the crate controller station and at the module stations to which they are dedicated.

This standard was reviewed and balloted by the Nuclear Instruments and Detectors Committee of the IEEE Nuclear and Plasma Sciences Society. Because of the board applicability of the CAMAC system, this standard was submitted for review to liaison representatives of numerous societies and committees including the Communications Society, Computer Society, Industry Applications Society, Industrial Electronics and Control Instrumentation Group, Instrumentation and Measurement Group, and the Power Generation and Nuclear Power Engineering Committees of the Power Engineering Society.

The revision of this standard was in conjunction with the 1981 review (1982 issue) of the entire family of IEEE CAMAC standards undertaken to incorporate existing addenda and corrections into the standards.