Puzzle 99 of 100

An odd number of ones

Goal

Make Q high while an odd number of the values of A taken on rising edges of CLK were high.

Die: 30 by 29 squares
Layers: Metal, Polysilicon, Contact, N active, P active, N well, Metal 2, Via
Inputs: CLK, CLKN, A
Output: Q
Supply: VDD, VDD
Ground: GND, GND

New in this puzzle

A running result

A flip-flop whose next value combines its own output with an input keeps a result over everything the input has delivered. Here it records whether the number of ones so far is odd.

Hint

The next Q is Q exclusive OR A. Feed D from switches controlled by Q and QN that pass A while Q is low and the inverse of A while Q is high, with an inverter for A. Switches controlled by A would fail, because A can change while CLK is low, when QN is only stored charge.

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 99, An odd number of ones, 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 99, An odd number of ones, 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 99, An odd number of ones, 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

Metal238 squares
Polysilicon53 squares
Contact35 squares
N active19 squares
P active19 squares
N well81 squares
Metal 2303 squares
Via46 squares
Input padCLK, CLKN, A
Output padQ
Supply padVDD, VDD
Ground padGND, GND
Squares you draw, change, or erase273 squares

About the drawing

The drawing uses 510 of the die's 870 squares.
Part of the drawing is in place when the puzzle opens. To finish it, paint 242 empty squares and change 31 drawn squares.
It forms 14 transistors: 7 N transistors and 7 P transistors. Each one is a place where polysilicon crosses active silicon.
35 contacts join metal to the polysilicon or active silicon under it.
46 vias join metal 2 to the metal under it.

Starting drawing for puzzle 99, An odd number of ones, on a numbered grid. — The drawing when the puzzle opens. The dashed outline marks the squares the solution changes.