Circuits: VLSI

Puzzle 29 of 100

Read the target

Goal

Make Y match its target. The goal does not name the gate: compare the target with A and B on the scope to find when Y is high.

Die
15 by 15 squares
Layers
Metal, Polysilicon, Contact, N active, P active, N well
Inputs
A, B
Output
Y
Supply
VDD
Ground
GND

Go to the solution

New in this puzzle

The target is the specification

The target band on the scope states what an output must do at every moment. Reading it against the inputs gives the truth table of the gate.

Hint

Y is low only while A is low and B is high. That is a NAND gate with the inverse of A as one of its inputs.

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 29, Read the target, 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 29, Read the target, 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 29, Read the target, 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

  • Metal70 squares
  • Polysilicon37 squares
  • Contact17 squares
  • N active8 squares
  • P active16 squares
  • N well52 squares
  • Input padA, B
  • Output padY
  • Supply padVDD
  • Ground padGND
  • Squares you draw, change, or erase99 squares

About the drawing

  • The drawing uses 127 of the die's 225 squares.
  • Part of the drawing is in place when the puzzle opens. To finish it, paint 97 empty squares and change 2 drawn squares.
  • It forms 6 transistors: 3 N transistors and 3 P transistors. Each one is a place where polysilicon crosses active silicon.
  • 17 contacts join metal to the polysilicon or active silicon under it.
Starting drawing for puzzle 29, Read the target, on a numbered grid.
The drawing when the puzzle opens. The dashed outline marks the squares the solution changes.