Free Timing Diagram Maker
Describe your digital signals or communication protocol and get a clear timing diagram in seconds. Perfect for SPI, I2C, UART, FPGA, and embedded systems documentation. No account needed.
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A timing diagram shows digital signals over time, capturing the precise sequence of clock edges, data transitions, control assertions, and timing relationships in a digital system. Whether you are documenting a communication protocol, specifying FPGA timing constraints, creating a chip datasheet figure, or reviewing firmware behavior, a clear timing diagram communicates the exact intended behavior. Our free timing diagram maker converts a plain-language description into a WaveDrom-style diagram with clock signals, logic levels, bus data labels, and annotated timing relationships.
How to make a timing diagram in 4 steps
Describe your signals
Type a description of your digital signals — name each signal (CLK, CS, MOSI, SDA, etc.), describe its type (clock, logic high/low, bus data, tri-state), and explain the transaction or sequence you want to show. Include timing relationships like setup and hold times if relevant.
Generate the diagram
Click Generate and the AI produces a WaveDrom-style timing diagram with clock waveforms, logic signals, bus stable and transition states, don't-care periods, and high-impedance (Z) states annotated where appropriate. Bus signals are labeled with data values.
Review timing relationships
Check that clock-to-data relationships are correct, chip-select assertion and deassertion timing relative to the clock is accurate, and that protocol-specific conditions (START, STOP, ACK in I2C; SS assertion in SPI) are correctly placed.
Export for documentation
Download the timing diagram for datasheets, application notes, firmware review documents, or FPGA timing specifications. No account or WaveDrom installation required.
What is a timing diagram?
A timing diagram is a waveform-based diagram that shows the state of digital signals over time. It is the standard tool for documenting and specifying the behavior of digital circuits, microprocessor buses, communication protocols, and FPGA interfaces. Every signal is drawn as a horizontal waveform — showing when it is high, low, transitioning, carrying stable data, in a don't-care state, or in high impedance — and the diagram reads left to right as time progresses.
The dominant open-source standard for timing diagrams is WaveDrom, which uses a JSON-based DSL (domain-specific language) to describe waveforms and renders them as SVG. WaveDrom defines signal types: 'p' for positive-edge clock, 'n' for negative-edge clock, '1' and '0' for logic high and low, '=' for bus stable data (with a label), 'x' for don't-care, and 'z' for high impedance. Edge relationships and annotations between signals can be drawn with arrows to indicate setup time, hold time, or propagation delay.
Timing diagrams are essential for documenting serial communication protocols. An SPI timing diagram shows the chip select (SS/CS) going low, the clock (SCLK) running at the configured polarity and phase (CPOL/CPHA), and data shifting out on MOSI while being sampled on MISO. An I2C timing diagram shows the START condition (SDA falls while SCL is high), the address byte with each bit, the ACK pull-down by the receiver, and the STOP condition. UART diagrams show the start bit, data bits (LSB first), parity, and stop bit framing.
Our free timing diagram maker is designed for digital hardware engineers, firmware developers, FPGA designers, and embedded systems engineers who need a clear waveform diagram quickly. Describe your signals and protocol in plain language and receive a properly structured timing diagram for your documentation, review, or datasheet.
Frequently asked questions
What is WaveDrom?
WaveDrom is an open-source JavaScript library and online editor for creating digital timing diagrams from a JSON description. It defines a standard signal type vocabulary (clock, logic, bus, don't-care, high-impedance) and renders clean SVG waveform diagrams. WaveDrom is widely used in chip datasheets, FPGA documentation, and protocol specifications. Our timing diagram maker uses the WaveDrom rendering conventions.
What is the difference between SPI and I2C timing?
SPI (Serial Peripheral Interface) is a four-wire full-duplex protocol with separate MOSI (master out), MISO (master in), SCLK (clock), and CS (chip select) signals. I2C (Inter-Integrated Circuit) is a two-wire half-duplex protocol using SCL (clock) and SDA (data) with open-drain signaling, START/STOP conditions, and ACK/NACK bits. SPI is faster and simpler; I2C supports multiple masters and devices on the same two wires.
What does high impedance (Z) mean on a timing diagram?
High impedance (Z) means a signal is neither driven high nor driven low — the driver is effectively disconnected from the bus. This state appears on shared buses where only one device drives the line at a time. In SPI, the MISO line is in high impedance when the selected slave is not actively responding. In I2C, the open-drain SDA and SCL lines are pulled high by resistors when no device is pulling them low.
What are setup time and hold time in a timing diagram?
Setup time is the minimum time a data signal must be stable before the active clock edge for the flip-flop or latch to reliably capture it. Hold time is the minimum time the data signal must remain stable after the active clock edge. Both are specified in the device datasheet and shown on timing diagrams with annotated arrows between the data signal transition and the clock edge.
Can I use this for FPGA timing documentation?
Yes. FPGA designers use timing diagrams to specify the intended behavior of interfaces before implementation and to document the actual behavior during verification. Describe your FPGA interface signals — clock, reset, valid, ready, data bus — and the transaction sequence, and the generator will produce a WaveDrom-style diagram you can include in your design specification or review document.
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