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1. (WO1985002922) IMPROVEMENTS IN OR RELATING TO COMPUTER SYSTEMS

Pub. No.:    WO/1985/002922    International Application No.:    PCT/GB1984/000446
Publication Date: Jul 4, 1985 International Filing Date: Dec 20, 1984
IPC: G06F 5/01
G06F 9/30
Applicants: HEMDAL, Goran, Anders, Henrik
Inventors: HEMDAL, Goran, Anders, Henrik
Title: IMPROVEMENTS IN OR RELATING TO COMPUTER SYSTEMS
Abstract:
Computer system having a central processing unit and a main memory for storage of information in binary form. A master control unit is provided for performing individual and selected range checking and selected range checking and range conversion by reading of information from an internal memory of the master controlled unit which contains a data Descriptor Table with a table entry for each individually accessible data element in the main memory with two elements of each Descriptor Table entry assigned for range check and conversion purposes. One of the elements permits one of the extreme limits of a value range of a data element in the main memory associated with a data Descriptor Table entry to be determined and the second element allows the number of values in the value range of the associated data element to be determined. There is also provided a set of arithmetic circuits interposed in the data path to and from the main memory to be utilised for each read or write of information to and from the main memory. Thus the arithmetic circuits receive their input from the main memory and from the data Descriptor Table entry for a data element and deliver their output to the central processor unit by reading of information from a main memory and also receive input from the central processor unit and the Data Descriptor Table entry for the data element and deliver a corresponding output to the main memory. The master control unit has means for generating an interrupt signal to the central processor unit in the case of an out of range value being detected.