Puzzle 51 of 100

A delay line

Goal

Make Y follow A about 7 ns late, as the target shows.

Die: 30 by 12 squares
Layers: Metal, Polysilicon, Contact, N active, P active, N well
Input: A
Output: Y
Supply: VDD
Ground: GND

New in this puzzle

Delay in stages

Each gate takes a little time to charge the gate it drives, so a signal arrives later at each stage of a chain. An even number of inverters keeps the signal the right way up, and the number of stages sets the delay.

Guide

Draw the outlined inverter and bring A to its gate. The contacts on the left of its gate line are strapped to the rails, and the contacts on the right are its output.
Draw three more inverters in the outlined places, each fed from the output of the one before it.
Join the last output to Y, and compare its edges with the target.

Hint

Each inverter delays its input a little, and two inverters in a row give the signal back the right way up. Draw four small inverters in a row from A, each output feeding the next gate, and join the last output to Y.

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 51, A delay line, 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 51, A delay line, 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 51, A delay line, 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

Metal134 squares
Polysilicon44 squares
Contact28 squares
N active12 squares
P active24 squares
N well76 squares
Input padA
Output padY
Supply padVDD
Ground padGND
Squares you draw, change, or erase150 squares

About the drawing

The drawing uses 210 of the die's 360 squares.
Part of the drawing is in place when the puzzle opens. To finish it, paint 150 empty squares.
It forms 8 transistors: 4 N transistors and 4 P transistors. Each one is a place where polysilicon crosses active silicon.
28 contacts join metal to the polysilicon or active silicon under it.

Starting drawing for puzzle 51, A delay line, on a numbered grid. — The drawing when the puzzle opens. The dashed outline marks the squares the solution changes.