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Selective Ring Modification with Check Pattern

IP.com Disclosure Number: IPCOM000085856D
Original Publication Date: 1976-Jun-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Stranko, T: AUTHOR [+2]

Abstract

A data processing system may include logic modules which contain shift rings, each consisting of a large number of shift register elements. In order to modify a given element in the ring, a common technique is to shift out the entire ring into a system storage, modify the appropriate bit, and shift the modified data back into the ring. This technique requires the execution of several instructions and wastes both system time and system storage.

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Selective Ring Modification with Check Pattern

A data processing system may include logic modules which contain shift rings, each consisting of a large number of shift register elements. In order to modify a given element in the ring, a common technique is to shift out the entire ring into a system storage, modify the appropriate bit, and shift the modified data back into the ring. This technique requires the execution of several instructions and wastes both system time and system storage.

The above situation is improved by the implementation of a selective shift or rotate ring instruction. If a particular ring has N bits in it and there is a need to examine bit X, the value X is set into a hardware counter, not shown. The system then issues a rotate ring instruction to the unit which contains the hardware counter as well as an n-bit shift register, causing data to be shifted bit- serially into the selected ring from the high-order bit of the shift register. At the same time that data shifts out of the n-bit shift register, new data shifts into its low-order position from the end of the ring.

When the counter, which decremented at each bit transfer, reaches zero the operation stops and the contents of the shift register can be put into a buffer register broadside or left in the shifter. Bit X will be in bit n-1 of the shift register and can be examined (or altered) by reading (or writing into) this register.

The ring is then reset to its original value by perform...