Stixu Stick Diagrammer

N pull-up or P pull-down detected. Simulation may be inaccurate.

Manage Terminals

Delete an Input

Add an Input

Place Terminal

Delete an Output

Add an Output

Paint/Erase

Terminals

Rows:

Cols:

Shift grid

Evaluate

Learn

Share and export

Settings

About

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Paint layers on the grid, place the terminals, then evaluate to get the circuit's truth table.

Drawing

Choose a layer with the colored circles: pdiff, ndiff, poly, metal1, metal2 or contact. Its name shows above the canvas.
Click or tap a cell to paint it. Drag to paint a straight line, horizontal or vertical.
With the contact layer selected, dragging moves a single contact instead of drawing a line.
Mouse: right-click a cell to clear every layer in it, or right-drag to clear a rectangle. Right-click an empty cell to switch to the next layer.
Touch: tap Paint/Erase to switch to erasing, then tap or drag to clear cells. Choosing a layer switches back to painting.
Undo and redo sit beside the Paint/Erase button, or use and .

How layers connect

Cells on the same layer connect to the cells above, below, left and right of them. Diagonal neighbors don't connect.
Different layers only connect through a contact, which joins every layer painted in its cell.
Poly crossing ndiff makes an NMOS transistor; poly crossing pdiff makes a PMOS. The diffusion must extend past the poly on at least two sides, and the crossing cell must not have a contact.
A cell can hold ndiff or pdiff, not both.
Stixu follows the stick-diagram abstraction: an NMOS only conducts low (logic 0) and a PMOS only conducts high (logic 1). An NMOS pull-up or PMOS pull-down never conducts, and evaluating shows a warning above the canvas.

Terminals

The terminals are VDD, GND, inputs (A, B, C, …) and outputs (Y, X, W, …). You can have up to eight inputs and outputs in total.
Keyboard: point at a cell and press to move VDD there, to move GND, or a terminal's letter, such as A or Y, to move that terminal.
Keyboard: and add and remove an input; and do the same for outputs.
Touch: tap Terminals . Use and on the left for inputs and on the right for outputs. To move a terminal, pick it from the list, tap , then tap a cell.
Erasing never removes a terminal's contact; move the terminal instead.

The grid

Use the Rows and Cols and buttons to grow or shrink the grid at its edge.
The Shift grid arrows move the whole drawing one cell, or use , , and .
Point at a cell and press or to insert or delete a column there, and or for a row.

Evaluating

Press or select Evaluate. On a phone, scroll down to find it.
The truth table has one row per input combination, with input A as the most significant bit.
Click or tap an output value to highlight the cells connected to that output for that row. For a conflict (X), the highlight may not show every conflicting path.

1: Driven high, by VDD or an input at 1
0: Driven low, by GND or an input at 0
Z: Not driven (floating)
X: Conflict: logic 1 and 0 are shorted together somewhere in the circuit
H: Possibly high: only a transistor with a floating gate could drive it, and only high
L: Possibly low: the same, but low
U: Unknown: floating gates could drive it high or low
?: Unstable: no stable logic value; occurs in circuits such as oscillators

Sharing and export

From the menu, copy a link that opens your drawing, or download it as Verilog or as IRSIM files.

Stixu is a tool for designing and validating CMOS logic circuits.

The tool was conceived and developed by Nick Overacker, an Oklahoma State University Computer Engineering graduate currently living in Japan.

The user interface was designed and implemented with the help of Miho Kobayashi, a Kansai Gaidai University graduate, former OSU exchange student, and freelance web designer.

The STIXU logo was designed by Sam the Designer, a freelance graphic designer based in Japan.

The default canvas palette was borrowed from Paul Tol's work.

The alternate "Sorcery" palette was inspired by the Magic VLSI layout tool.