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Indirect Addressing Accommodation For Unswitchable Bits

IP.com Disclosure Number: IPCOM000095443D
Original Publication Date: 1964-Jan-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Heilweil, MF: AUTHOR

Abstract

Choosing address values so that unswitchable bits provide valid address data allows locations in memory having unswitchable bits to control indirect addressing. Such is to preselected perfect locations even though the indirect address fields contain unswitchable bits.

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Indirect Addressing Accommodation For Unswitchable Bits

Choosing address values so that unswitchable bits provide valid address data allows locations in memory having unswitchable bits to control indirect addressing. Such is to preselected perfect locations even though the indirect address fields contain unswitchable bits.

An auxiliary bit plane provides each memory word with an auxiliary bit to indicate by a 1 the presence of a fault in that word. As a part of manufacturing testing, those locations of the memory having unswitchable bits are determined and the auxiliary bits set to the 1 value. At this time, the unswitchable bits are determined and a set of addresses is generated in which the unswitchable bits are acceptable. An unswitchable 0 provides an acceptable 0 value. An unswitchable 1 provides an acceptable 1 value. Unswitchable bits are identified by rectangles drawn about the bit value. A fairly compact set of addresses can be generated to include unswitchable bits as in the example shown. The actual bit values are shown in the indirect address field with the decimal equivalent in the adjacent column in parentheses. Address value 0 11 01 (13) is not impaired by the unswitchable nature of the adjacent 1 bits. The indirect addressing mechanism can be standard, so long as there is regeneration of the auxiliary bit and of the address field. The auxiliary bit can also be set by the operator to perform indirect addressing. Care must be taken in this operation...