A Contents Addressable Analyser for One Million Channels

Abstract

A hardware analyser based on the zone selection technique has been constructed. It has an input dead time of 10 μ.seconds and will analyse 4096 channels, in 256 zones of 16 channels from a million channel field. The input 20-bit descriptor is divided into the 16 most significant bits to form the Zone Code, specifying the zone within the field, and the 4 least significant bits to form the Channel Code, specifying the channel in the zone. Zone Codes are held in a 256 word 16-bit transfluxor contents addressable store which enables the storage location occupied by any Zone Code to be found in a single operation. The methods of loading, comparing and reading out codes are described. Each location in the transfluxor store is allotted a 16 word block in a conventional 4096 word 20-bit core store. The specific location in this block at which the count is to be stored is specified by the Channel Code. The live display includes map, section and an 'isometric' projection which may be rotated or tilted. This latter display, though geometrically accurate to 2%, uses simple circuitry with linear potentiometers. Both display and data collection may be confined to selected areas of the data field. In the limit this area may be reduced to 64 × 64 channels giving a total analysis of 4096 adjacent channels within a field of, for example, 1024 × 1024 channels. Automatic selection of descriptors on the basis of counts accumulated is also provided.