Puzzle 44 of 100

Choose an output

Goal

Make Y follow A while S is low, and Z follow A while S is high. The output that is not chosen must be low.

Die: 17 by 13 squares
Layers: Metal, Polysilicon, Contact, N active, P active, N well
Inputs: SN, A, S
Outputs: Y, Z
Ground: GND, GND

New in this puzzle

Holding a line low

An output whose switch is open is driven by nothing, so it keeps whatever level it had. An N transistor to GND that conducts only while the switch is open gives the output a defined low level instead.

Hint

The two transmission gates are drawn. Add an N transistor from each output to GND that conducts while that output's switch is open: one from Y with its gate on S, and one from Z with its gate on SN.

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 44, Choose an output, 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 44, Choose an output, 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 44, Choose an output, 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

Metal41 squares
Polysilicon47 squares
Contact14 squares
N active20 squares
P active10 squares
N well30 squares
Input padSN, A, S
Output padY, Z
Ground padGND, GND
Squares you draw, change, or erase19 squares

About the drawing

The drawing uses 109 of the die's 221 squares.
Part of the drawing is in place when the puzzle opens. To finish it, paint 19 empty squares.
It forms 6 transistors: 4 N transistors and 2 P transistors. Each one is a place where polysilicon crosses active silicon.
14 contacts join metal to the polysilicon or active silicon under it.

Starting drawing for puzzle 44, Choose an output, on a numbered grid. — The drawing when the puzzle opens. The dashed outline marks the squares the solution changes.