Browse Prior Art Database

Protection of Memories on a Word Basis

IP.com Disclosure Number: IPCOM000095991D
Original Publication Date: 1964-Nov-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Evans, J: AUTHOR [+3]

Abstract

The circuit protects individual words stored in main memory 10. The address of each word to be protected is stored in adjunct memory 12. Address transform circuit 14 is of a type such that each input address applied to it causes an output address to be generated. This is the address in memory 12 at which an entry for the given input address would be stored if such address were contained in it. Each entry in memory 12 also contains a protect key which, e. g., indicates the user who has access to the particular word. The protect key for the particular program being used is stored in circuit 16.

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Protection of Memories on a Word Basis

The circuit protects individual words stored in main memory 10. The address of each word to be protected is stored in adjunct memory 12. Address transform circuit 14 is of a type such that each input address applied to it causes an output address to be generated. This is the address in memory 12 at which an entry for the given input address would be stored if such address were contained in it. Each entry in memory 12 also contains a protect key which, e. g., indicates the user who has access to the particular word. The protect key for the particular program being used is stored in circuit 16.

In operation, a memory address applied to MAR 18 causes the corresponding word in memory 10 to be read out into data register 20 and also causes the word in memory 12 resulting from the address transformation in circuit 14 to be read out into register 22. The address read into register 22 is compared with the address in MAR in compare circuit 24. If these two addresses are equal, an output signal is generated on line 26. The protect key read into register 22 is compared with the protect key in circuit 16 in compare circuit 28. An output signal is generated on line 30, if these two protect keys are not equal. The combined occurrence of a signal on line 26 and on line 30 fully conditions And 32 to generate an output signal on line 34, indicating that the address in MAR is to be protected.

Under these conditions, gate 36 is conditioned to...