Multiple Alarms: Major Goals and Cryogenic Controls Implementation

B. Lublinsky
Fermi National Accelerator Laboratory

It is a very common situation when controlled hardware can work in the variety of different regimes, in which case the control system has to have certain amount of intelligence to be able to recognize the regime change and reconfigure itself accordingly. One of the crucial points here is being able to reconfigure the alarm system, so that it behaves appropriately through all possible regimes of equipment functioning. In practice it usually involves three major parts:

- regime determination support;
- regime switching support;
- multiple alarms support.

The paper deals with the implementation of the multiple alarms support for the cryogenic controls system. In this system a dedicated finite state machine (FSM) is used for tracking of the cryogenic system parameters and determining of the current regime. This FSM is switching internal "regime" variable inside each FRIG microprocessor. Multiple alarm blocks, specifying alarms and limits for different regimes on a device by device basis, are stored in the microprocessor memory. These alarm blocks are indexed by the "regime" variable, so that regime change automatically triggers the appropriate alarm block to be used in the alarm calculations.

Additional changes have been implemented in other parts of ACNET for storing multiple alarm blocks in the database, do multiple alarms downloading, perform save/restore and another ACNET functions. Multiple alarms are now completely operational and are used in the debugging mode in the cryogenic control system.