Browse Prior Art Database

Memory Page Address Override

IP.com Disclosure Number: IPCOM000085103D
Original Publication Date: 1976-Feb-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Dumstorff, EF: AUTHOR [+3]

Abstract

Memory page selection signals normally resulting from decoding bits from a page pointer register are overridden by decoding page pointer bits, taken from the address register when the instruction register furnishes address bits. This arrangement enables switching between pages without requiring instructions to change the contents of the page pointer register back and forth.

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Memory Page Address Override

Memory page selection signals normally resulting from decoding bits from a page pointer register are overridden by decoding page pointer bits, taken from the address register when the instruction register furnishes address bits. This arrangement enables switching between pages without requiring instructions to change the contents of the page pointer register back and forth.

Memory 10 is shown as containing four pages, each page having 256 addressable storage positions. Address register 15 is connected to receive eight bit addresses from sources, not shown. These address bits (0-7) are applied to AND circuit 16 for addressing the storage positions of any selected page via OR circuit 17. AND circuit 16 is controlled by a signal on line 18 which is present for all instructions, using page pointer bits from page pointer register 20.

Register 20 is loaded under program control with two bits (bits 6 and 7) from register 15 via AND circuit 21. AND circuit 21 is controlled by a program control signal on line 22. The contents of register 20 are selectively gated via AND circuit 23 and OR circuit 24 to decode circuit 25. AND circuit 23 is controlled by the signal on line 18. Decode circuit 25 develops four page select signals from the two bits passed by OR circuit 24. Hence, the contents of the page pointer register 20 select the page and the contents of the address register 15 select the particular storage position within the selected page for...