Puzzle 46 of 100

One line, two drivers

Goal

Make Y the inverse of A while S is low, and the inverse of B while S is high. The two drivers share the line Y.

Die: 16 by 29 squares
Layers: Metal, Polysilicon, Contact, N active, P active, N well
Inputs: S, A, B
Output: Y
Supply: VDD, VDD
Ground: GND

New in this puzzle

One driver at a time

Several drivers can share one line as long as only one of them is on at any moment. Two drivers that are on together fight, and the line settles between the two levels.

Hint

The driver for A is drawn in the upper row and drives only while S is low. Draw a second tri-state inverter for B in the lower row that drives only while S is high, with its P enable gate on the inverse of S and its N enable gate on S. Both signals already reach the lower row under the shared GND rail.

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 46, One line, two drivers, 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 46, One line, two drivers, 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 46, One line, two drivers, 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

Metal112 squares
Polysilicon79 squares
Contact25 squares
N active15 squares
P active30 squares
N well100 squares
Input padS, A, B
Output padY
Supply padVDD, VDD
Ground padGND
Squares you draw, change, or erase68 squares

About the drawing

The drawing uses 243 of the die's 464 squares.
Part of the drawing is in place when the puzzle opens. To finish it, paint 67 empty squares and change 1 drawn square.
It forms 10 transistors: 5 N transistors and 5 P transistors. Each one is a place where polysilicon crosses active silicon.
25 contacts join metal to the polysilicon or active silicon under it.

Starting drawing for puzzle 46, One line, two drivers, on a numbered grid. — The drawing when the puzzle opens. The dashed outline marks the squares the solution changes.