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The Detector Memory System

The Detector Memory System allows detector data to be collected, displayed and transferred to the system computer. A detailed description of the system is given by Johnson 1986 (Electronics report 413, the Detector Memory System).

The DMS is a purpose-built computer, based upon a Motorola 68020 microprocessor, with a large area of memory (128 Mbytes) for storage of detector data. The system design is based on the industry--standard VME architecture. There is a high speed data interface (DICI; Dual IPCS CCD Interface) between the detectors and the VME memory. The system also has an image display facility, based on an Opal Graphics Controller.

Immediately after each exposure the data from all detectors appears in memory in the Detector Memory System (DMS). Images obtained with CCD detectors are read out into the DMS at the end of an exposure. Photon counts from the IPCS--2 are continually transferred to the DMS during an exposure, where they are built up into an image.

The DMS is capable of handling multiple detectors simultaneously, reading the data from different detectors into different areas of memory (normally referred to as buffers). This feature is particularly important for the operation of ISIS.