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# Implementation of the Function "Two of N Signals Are On"

IP.com Disclosure Number: IPCOM000099977D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 64K

IBM

## Related People

Weinberger, A: AUTHOR

## Abstract

The function "two of N signals are on" is implemented as follows: 1. The N signals are partitioned into groups, each group generating the subfunctions, "none on", "one on" and "two on". 2. The subfunctions of two or more groups are combined to generate the same subfunctions of the larger group. 3. Step 2 is repeated until the group includes all N signals. Then, only the "two on" subfunction is generated, representing the desired function.

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Implementation of the Function "Two of N Signals Are On"

The function "two of N signals are on" is implemented as
follows:
1.   The N signals are partitioned into groups, each group generating
the subfunctions, "none on", "one on" and "two on".
2.   The subfunctions of two or more groups are combined to generate
the same subfunctions of the larger group.
3.   Step 2 is repeated until the group includes all N signals.
Then, only the "two on" subfunction is generated, representing the
desired function.

Figure 1 shows 72 signals (S1,...,S72), partitioned into 9
groups of 8 signals.  Each group generates three subfunctions of
macro M1 according to Figure 2.  The outputs of three M1 macros are
combined to generate three subfunctions of macro M2 of the larger
group now comprised of 24 signals, as per Figure 3.  Finally, the
three larger groups are combined to generate only the subfunction
"two on" (according to the last equation of Figure 3 with appropriate
variables) to represent the final function "two of 72 are on".  The
equations for the M2 outputs are shown in both true and complement
form.