What is 1ps in Verilog Timescale? Time Units, Resolution, & Examples

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Learn the dos and don'ts for using 1 picosecond (1ps) in Verilog

Co-authored by Carmine Shannon Reviewed by Luigi Oppido

Last Updated: September 5, 2025 Fact Checked

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What does 1ps mean?

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How to Use Verilog Timescale

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Other Meaning of 1ps

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Tips

1ps is a unit of measurement in the Verilog timescale compiler directive. It stands for 1 picosecond, or 1 trillionth of a second. The `timescale directive, which determines the unit of time for a simulation and rounds the outputs, can be tricky, so keep reading to see how to set up a module and record outputs in Verilog.

1ps in Verilog Timescale

1ps stands for 1 picosecond, which is equal to 1 trillionth of a second, and refers to one unit in Verilog timescale. The `timescale directive is written as `timescale [time unit]/[resolution]. The first unit sets the timescale of the module, and the resolution sets how far the outputs are rounded.

Section 1 of 3:

What does 1ps mean?

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1ps stands for 1 picosecond. The abbreviation “ps” means picosecond, or 1/10¹² (1 trillionth) of a second. In the programming language Verilog, 1ps is a unit for the `timescale compiler directive, which sets the default unit of time for a simulation and the resolution to which outputs are rounded.^{[1]
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- The units are seconds (s), milliseconds (ms), microseconds (us), nanoseconds (ns), picoseconds (ps), and femtoseconds (fs).

Section 2 of 3:

How to Use the Verilog Timescale Directive

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1
Choose your units of time and resolution. In Verilog, the timescale directive is written as `timescale integer [time unit] / integer [resolution]. When choosing your units, always put the larger one first. The general time scale must be divisible by the resolution.^{[2]
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- The first unit is how time is measured, and the second is how precise your recordings are.^{[3]
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- The ` symbol, or backtick, lets the program know that you’re using a compiler directive. It introduces the `timescale directive, as well as `include, `resetall, `define, and others.^{[4]
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2
Choose your integers (order of magnitude). Finish setting the timescale by choosing one of three integers to put before your units: 1, 10, or 100. By adding an integer you can control how much time makes up a single unit or how many units go into the resolution.
- For example, if you write the directive `timescale 10ns / 1ns, then for every 10 nanoseconds the output value will be rounded to the nearest nanosecond.
- A common timescale is 1ns / 1ps, which means at each nanosecond there is an output rounded to the nearest picosecond.
3
Write your test bench module. Test benches run a simulation of your design, and check the outputs. Set up your module by writing:
- `timescale [unit of time]/[unit of precision]
- module tb;
- reg val;
- initial begin
- val<=[where you want to start];
4
Set delays by writing #[real number] before your functions. To program when your data is recorded, write the operator #[real number] and then a function. The operator # (AKA the delay) is multiplied by the time unit, then rounded to the nearest time precision unit (resolution). For example, you could write
- #5 $display (“T=%0t At time #5”, $realtime);
- val<=1;
- If your `timescale is 1ns/1ns, then your output would be 1(ns) * 5 = 5 since it’s rounded to the nearest nanosecond.
- If your `timescale was 10ns/1ns, then your output would be 10(ns) * 5 = 50.
- If your `timescale was 1ns/1ps, then your output would be 1000ps (AKA 1ns) * 5 = 5000 to convert it to picoseconds.
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Set the end time and add the ending code. To end the simulation, write #[real number] before the function $display (“T=%0t End of simulation”, $realtime); then write the codes “end,” then “endmodule”. “End” closes the block “initial begin,” and “endmodule” closes the “module” block.
- Your entire simulation may look like this:
  - `timescale 1ns/1ps
  - module tb;
  - reg val;
  - initial begin
  - val<=0;
  - #1 $display (“T=%0 At time #1”, $realtime);
  - val<=1;
  - #5 $display (“T=%0t End of simulation”, $realtime);
  - end
  - endmodule

Section 3 of 3:

Other Meaning of 1ps

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Video games that are in first-person perspective are often called first-person shooters, more often abbreviated as FPS. Occasionally, they’re also abbreviated to “1ps.”
Sometimes, IPS refers to a unit of measurement for acceleration, which is inches per second.^{[5]
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Research source} When it’s being used for a change in velocity (acceleration), it’s written as inches per second².
IPS (in-plane switching) monitors are a kind of LCD screen where liquid crystals are sandwiched between two planes of glass.^{[6]
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IPS can also mean “intrusion prevention systems,” which block attacks on networks and computers.^{[7]
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