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Circuit Structures To Eliminate Or Reset Dynamic Carry Storage Loops

IP.com Disclosure Number: IPCOM000095423D
Original Publication Date: 1964-Jan-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Hartman, FB: AUTHOR

Abstract

This adder-subtractor employs 1's complement operation with spurious signals being developed by end-around carry loops. This is when all positions are set to propagate during subtraction operation. The elimination of spurious signals is with little or no delay to the add or subtract operation.

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Circuit Structures To Eliminate Or Reset Dynamic Carry Storage Loops

This adder-subtractor employs 1's complement operation with spurious signals being developed by end-around carry loops. This is when all positions are set to propagate during subtraction operation. The elimination of spurious signals is with little or no delay to the add or subtract operation.

Adder-subtractor 10 has conventional adder positions 20, 30, 40... n 0, where n is an integer defining the high-order position, and an end-around loop 12. A closed loop of unity gain is established when all storage positions are set to propagate which is defined as one and only one operand bit present. The loop is capable of storing information. Information set into the loop may provide an erroneous output in a subsequent subtraction operation. For addition, however, the end-around carry loop is open-circuited at the beginning of the operation. This destroys any information in the loop that could render the operation erroneous.

In a subtraction operation, spurious signals are eliminated by applying an appropriately timed negative clearing pulse to an input 22 connected to a plurality of And's 25...n5 included in the end-around carry loop 12. The clearing pulse is initiated at the beginning of the subtraction operation and simultaneously with the application of the operand inputs to their appropriate positions.

The clearing pulse is set to terminate before the carry signals appear in the carry circuits. The...