Circuits: VLSI

Puzzle 11 of 100

A switch made by crossing

Goal

Make Y follow A only while C is high.

Die
12 by 8 squares
Layers
Metal, Polysilicon, Contact, N active
Inputs
C, A
Output
Y

Go to the solution

New in this puzzle

N active silicon

Where polysilicon crosses N active silicon, a transistor forms. It is a switch: it joins the silicon on its two sides while the polysilicon is high.

Guide

  1. Paint metal from A and from Y toward the middle, leaving five empty squares between them.
  2. Choose N Active and fill those five squares.
  3. Place a contact on each end of the active silicon, so that it joins the metal.
  4. Place a contact under C, then paint polysilicon from it down across the active silicon and one square past it.
  5. Watch the scope. Y follows A only while C is high.

Hint

Paint N active silicon between two contacts on the path from A to Y, then cross it with polysilicon from C. Where polysilicon crosses active silicon, a transistor forms.

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 11, A switch made by crossing, 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 11, A switch made by crossing, 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 11, A switch made by crossing, 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.

Legend

  • Metal11 squares
  • Polysilicon5 squares
  • Contact3 squares
  • N active5 squares
  • Input padC, A
  • Output padY

About the drawing

  • The drawing uses 17 of the die's 96 squares.
  • The die starts empty, so you draw every square.
  • It forms 1 transistor: 1 N transistor. Each one is a place where polysilicon crosses active silicon.
  • 3 contacts join metal to the polysilicon or active silicon under it.