Puzzle 57 of 100

A slower ring

Goal

Make Y repeat with a period between 22.5 and 27 ns once EN is high.

Die: 40 by 15 squares
Layers: Metal, Polysilicon, Contact, N active, P active, N well
Input: EN
Output: Y
Supply: VDD
Ground: GND

New in this puzzle

Stages and period

A change goes around a ring twice in each period, once rising and once falling. Each stage added to the ring adds its delay twice, so the period grows in steps.

Hint

The ring closes after the second inverter, and the inverters after it only pass the signal on to Y. Close the ring after a later inverter instead, keeping the number of inverting stages in the ring odd. Each pair of stages added lengthens the period by about 6 ns.

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 57, A slower ring, 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 57, A slower ring, 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 57, A slower ring, 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

Metal241 squares
Polysilicon110 squares
Contact61 squares
N active26 squares
P active52 squares
N well152 squares
Input padEN
Output padY
Supply padVDD
Ground padGND
Squares you draw, change, or erase31 squares

About the drawing

The drawing uses 403 of the die's 600 squares.
Part of the drawing is in place when the puzzle opens. To finish it, paint 21 empty squares, change 5 drawn squares, and erase 5 squares.
It forms 18 transistors: 9 N transistors and 9 P transistors. Each one is a place where polysilicon crosses active silicon.
61 contacts join metal to the polysilicon or active silicon under it.

Starting drawing for puzzle 57, A slower ring, on a numbered grid. — The drawing when the puzzle opens. The dashed outline marks the squares the solution changes.