A local area computer for data acquisition and control

A low-cost control and data acquisition computer system for accelerators was developed to be used in distributed-architecture control systems. This local area computer (LAC) can be viewed as a low-cost replacement for the CAMAC crate and its associated computer. It is based on the STD bus backplane, a low-end industrial standard and currently runs on a 8088-based processor card. Communication with other computers on the system is achieved through a specially designed small-computer-system-interface (SCSI)-Ethernet controller, which can be programmed to allow data transmission only during a specific time slot. This mechanism avoids network delays due to collisions and enables the LAC to dump its entire database at regular intervals for retrieval by one or several hosts. Software, written in C and running under the VRTX real-time executive, mimics the easy access to hardware typical of CAMAC modules, allowing interfacing to control system software developed at other laboratories. Most of the LAC components are off-the-shelf items. However, some peripherals specific to accelerators, such as high-stability voltage references and charge analog-to-digital converters, were developed in-house