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# Multifunction Logic Circuit

IP.com Disclosure Number: IPCOM000094991D
Original Publication Date: 1965-Aug-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 3 page(s) / 26K

IBM

## Related People

Waxman, R: AUTHOR

## Abstract

These circuits provide the And, Or, Exclusive-Or, and latch functions in accordance with selective application of input levels and choice of output terminals.

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Multifunction Logic Circuit

These circuits provide the And, Or, Exclusive-Or, and latch functions in accordance with selective application of input levels and choice of output terminals.

Each Nand circuit 10, 12 and 14 produces a down output only when all of its inputs are at the up level. Nands 10 and 12 are connected in a latch configuration via feedback conductors 16 and 18 respectively.

Each Nand is provided with a plurality of inputs. Inputs A and B are applied to Nand 10 and C and D to Nand 12. The circuit's output is taken either from output terminals 20 and 22 or 24 or in special cases, all three.

To perform the And function for two variables, the first variable is applied to A and C. The second variable is applied to B and D. If both variables are at the up level, one Nand 10 or 12 is caused to have its output at the up level while the other provides a down output. It is immaterial which Nand 10 or 12 provides the up level output. This is because the inputs into Nand 14 are different and thus force the output of terminal 24 to be at the up level indicating the And function. If the two variable inputs are at different logical levels, then both Nand's 10 and 12 provide up levels. Such causes Nand 14 to provide a down output at terminal 24. The same effect occurs if both variables are at the down level.

To provide the Or function, the first variable is applied in common to A and B. The second variable is applied in common to C and
D. In this case, an Inclusive-Or function is performed at terminal 24 since Nand 14 is caused to produce a down output only when both input variables are at the down level

To perform the Exclusive-Or function requires the presence of both true and complement input variable levels. The first input variable has its true level applied to A and its complement level applied to C. The true level of the se...