A Standard Approach to Data Acquisition

A typical data acquisition system may have about a dozen front-end readout cards in each crate and these cards could be read out with a general purpose micro-processor. Data could be assembled via a vertical bus interface in each individual crate and transferred to a master readout crate.

There are several disadvantages of this approach for an experiment with the constraints of ZEUS [5].

• The vertical bus can form a bottle-neck, since the interference of traffic on the bus for the different tasks is difficult to avoid.
• The communication between neighbouring parts of a sub-detector is almost impossible.
• The system is in-flexible and re-wiring the interconnections can be problematic.
• The functions of control, triggering and data acquisition are difficult to combine because of the slow task-switching time of conventional processors.
• Inter-processor communication and down-loading is usually not supported in hardware and therefore requires complicated additional software, such as, a real-time distributed operating system.
• The use of ROM is difficult to avoid since the down-loading task is often not supported in hardware.
• A great deal of training and education is required to obtain the necessary expertise to effectively use the complicated support software.