Circuits: VLSI

Puzzle 97 of 100

Every fourth clock

Goal

Make Y high for one clock period in every four, while the count on Q1 and Q0 is 1.

Die
33 by 31 squares
Layers
Metal, Polysilicon, Contact, N active, P active, N well, Metal 2, Via
Inputs
CLK, CLKN
Outputs
Q0, Q1, Y
Supply
VDD, VDD
Ground
GND, GND

Go to the solution

New in this puzzle

Decoding a state

A gate that recognizes one combination of a counter's outputs is high in one state of each cycle. It turns a counter into a source of evenly spaced pulses.

Hint

The ripple counter is drawn. Y is Q0 AND NOT Q1, which a NOR gate of QN0 and Q1 gives.

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 97, Every fourth clock, 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 97, Every fourth clock, 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 97, Every fourth clock, 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

  • Metal279 squares
  • Polysilicon74 squares
  • Contact47 squares
  • N active27 squares
  • P active27 squares
  • N well111 squares
  • Metal 2384 squares
  • Via60 squares
  • Input padCLK, CLKN
  • Output padQ0, Q1, Y
  • Supply padVDD, VDD
  • Ground padGND, GND
  • Squares you draw, change, or erase71 squares

About the drawing

  • The drawing uses 620 of the die's 1023 squares.
  • Part of the drawing is in place when the puzzle opens. To finish it, paint 65 empty squares and change 6 drawn squares.
  • It forms 20 transistors: 10 N transistors and 10 P transistors. Each one is a place where polysilicon crosses active silicon.
  • 47 contacts join metal to the polysilicon or active silicon under it.
  • 60 vias join metal 2 to the metal under it.
Starting drawing for puzzle 97, Every fourth clock, on a numbered grid.
The drawing when the puzzle opens. The dashed outline marks the squares the solution changes.