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Learn the dos and don'ts for using 1 picosecond (1ps) in Verilog
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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.
Steps
Section 2 of 3:
How to Use the Verilog Timescale Directive
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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] X Research source
- The first unit is how time is measured, and the second is how precise your recordings are. [3] X Research source
- 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] X Research source
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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. [5] X Research source 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. [6] X Research source
- A common timescale is 1ns / 1ps, which means at each nanosecond there is an output rounded to the nearest picosecond.
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Write your test bench module. Test benches run a simulation of your design, and check the outputs. [7] X Research source 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];
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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). [8] X Research source 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. [9] X Research source
- 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
- Your entire simulation may look like this:
![Step 4 Set delays by writing #[real number] before your functions.](#/Image:1ps-Meaning-Step-5.jpg)
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Section 3 of 3:
Other Meaning of 1ps
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1ps can mean first-person shooter when referring to gaming. 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.”
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In math, IPS stands for inches per second. Sometimes, IPS refers to a unit of measurement for acceleration, which is inches per second. [10] X Research source When it’s being used for a change in velocity (acceleration), it’s written as inches per second 2 .
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IPS can also refer to a kind of LCD screen. IPS (in-plane switching) monitors are a kind of LCD screen where liquid crystals are sandwiched between two planes of glass. [11] X Research source
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IPSs are a kind of computer security system. IPS can also mean “intrusion prevention systems,” which block attacks on networks and computers. [12] X Research source
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References
- ↑ https://fpga.mit.edu/6205/_static/F23/documentation/1800-2017.pdf
- ↑ https://fpga.mit.edu/6205/_static/F23/documentation/1800-2017.pdf
- ↑ https://fpga.mit.edu/6205/_static/F23/documentation/1800-2017.pdf
- ↑ https://verilogams.com/refman/basics/directives.html
- ↑ https://www.javatpoint.com/verilog-timescale
- ↑ https://www.javatpoint.com/verilog-timescale
- ↑ https://www.javatpoint.com/verilog-timescale
- ↑ https://www.javatpoint.com/verilog-timescale
- ↑ https://www.javatpoint.com/verilog-timescale
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