Puzzle 96 of 100

Two ones in a row

Goal

Make Y high while the last two values of A taken on rising edges of CLK were both high.

Die: 35 by 29 squares
Layers: Metal, Polysilicon, Contact, N active, P active, N well, Metal 2, Via
Inputs: CLK, CLKN, A
Output: Y
Supply: VDD, VDD
Ground: GND, GND

Go to the solution

New in this puzzle

Remembering the input

A shift register keeps the last few values of its input, one in each flip-flop. A gate on their outputs recognizes a pattern in that recent history.

Hint

The flip-flops keep the last two values of A: Q0 the newer and Q1 the older. Y is Q0 AND Q1, which a NOR gate of QN0 and QN1 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 96, Two ones in a row, 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 96, Two ones in a row, 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 96, Two ones in a row, 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

Metal228 squares
Polysilicon74 squares
Contact47 squares
N active27 squares
P active27 squares
N well111 squares
Metal 2339 squares
Via56 squares
Input padCLK, CLKN, A
Output padY
Supply padVDD, VDD
Ground padGND, GND
Squares you draw, change, or erase87 squares

About the drawing

The drawing uses 549 of the die's 1015 squares.
Part of the drawing is in place when the puzzle opens. To finish it, paint 81 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.
56 vias join metal 2 to the metal under it.

Starting drawing for puzzle 96, Two ones in a row, on a numbered grid. — The drawing when the puzzle opens. The dashed outline marks the squares the solution changes.