Use of VME computers for the data acquisition system of the PHOENICS experiment

The data acquisition program PHON (PHOENICS ONLINE) for the PHOENICS-experiment at the stretcher ring ELSA in Bonn is described. PHON is based on a fast parallel CAMAC readout with special VME-front-end-processors (VIP) and a VAX computer, allowing comfortable control and programming. Special tools have been developed to facilitate the implementation of user programs. The PHON-compiler allows to specify the arrangement of the CAMAC-modules to be read out for each event (camaclist) using a simple language. The camaclist is translated in 68000 Assembly and runs on the front-end-processors, making high data rates possible. User programs for monitoring and control of the experiment normally require low data rates and therefore run on the VAX computer. CAMAC operations are supported by the PHON CAMAC-Library. For graphic representation of the data the CERN standard program libraries HBOOK and PAW are used. The data acquisition system is very flexible and can be easily adapted to different experiments. (orig.)