Puzzle 37 of 100

Majority

Goal

Make Y high while at least two of A, B, and C are high.

Die: 17 by 19 squares
Layers: Metal, Polysilicon, Contact, N active, P active, N well
Inputs: A, B, C
Output: Y
Supply: VDD
Ground: GND

New in this puzzle

A mirror gate

Inverting all three inputs of a majority gate inverts its result. Because of this, its P transistors can follow the same pattern as its N transistors, and the two strips look alike.

Hint

The gate lines are drawn in the order B, A, C, B, A. Draw the N strip so that it pulls low while A and B are both high, or while C and either A or B are high. The P strip uses the same pattern, and the inverter restores the polarity.

Solution

This is the game's reference drawing for the puzzle. It meets the goal and passes the design rules. Other drawings can pass as well.

Top View of the solved die for puzzle 37, Majority, with the Side View below it. — Top View of the solved die, captured from the game. Paths that carry a high level at the moment shown are lit. The Side View below cuts through the row between the dashed lines.

The game window in Isometric View with the solved die for puzzle 37, Majority, the guide, and the scope. — The whole game window in Isometric View. The scope on the right compares each output with its target band, and the message above it confirms that the drawing passes.

Solution drawing for puzzle 37, Majority, drawn on a numbered grid with every layer in its game color and pattern. — The solution on the grid. Squares are numbered from the top left corner, so you can count them. The dashed outline marks the squares you draw, change, or erase; the rest is drawn when the puzzle opens.

Legend

Metal127 squares
Polysilicon88 squares
Contact27 squares
N active14 squares
P active28 squares
N well68 squares
Input padA, B, C
Output padY
Supply padVDD
Ground padGND
Squares you draw, change, or erase91 squares

About the drawing

The drawing uses 219 of the die's 323 squares.
Part of the drawing is in place when the puzzle opens. To finish it, paint 55 empty squares and change 36 drawn squares.
It forms 12 transistors: 6 N transistors and 6 P transistors. Each one is a place where polysilicon crosses active silicon.
27 contacts join metal to the polysilicon or active silicon under it.

Starting drawing for puzzle 37, Majority, on a numbered grid. — The drawing when the puzzle opens. The dashed outline marks the squares the solution changes.