What does timescale 1ns 1ps mean in Verilog?
`timescale 1ns/1ps means that all the delays that follow (like# 5.1234) are interpreted to be in nanoseconds and any fractions will be rounded to the nearest picosecond (5123ps). However, all delays are represented as integers. The simulator knows nothing about seconds or nanoseconds, only unit-less integers.
What is timescale compiler directive?
The `timescale compiler directive specifies the default time unit and precision for all design elements that follow this directive and that do not have timeunit and timeprecision constructs specified within the design element.
What is the limitation of timescale directive?
P.S : The `timescale directive only affects the current compilation unit; it does not span multiple compilation units .
What is time delay Verilog?
The delays declaration can contain up to three values, such as rise, fall, and turn-off delays. The time taken for the output of a gate to change from some value to 1 is called a rise delay. The time taken for the output of a gate to change form some value to 0 is called a fall delay.
What is the default timescale in Verilog?
alu gets a timescale of 1ns/1ps because it was the last directive that stayed valid until the compiler found alu definition insisted of placing it in a different file. The des gets a timescale of 1ns/10ps because the directive was replaced before its definition.
What is the difference between $time and realtime?
Since your time scale is 10ns, $realtime returns 1.6 and $time has to return an integer, so that gets rounded up to 2. Your timescale is 1ns, so the %t format will scale the value to represent nanoseconds, it multiplies the returned value by 10. Try changing %t to %g to see what is going on.
What is time precision Verilog?
The time precision tells the smallest delay you can configure in a given time unit. Precision represent how many decimal points of precision to use relative to the time units. For example: timescale 100ps/10ps shall have a #1 delay of 100ps while you can give #0.1 as the smallest delay i.e. of 10ps.
What is the unit of delay?
The Unit Delay block holds and delays its input by the sample period you specify. When placed in an iterator subsystem, it holds and delays its input by one iteration. This block is equivalent to the z-1 discrete-time operator. The block accepts one input and generates one output. Each signal can be scalar or vector.
What are the data types in Verilog?
Verilog supports only predefined data types. These include bits, bit-vectors, memories, integers, reals, events, and strength types. These define the domain of description in Verilog.
What is time unit and time precision in Verilog?
The time_unit is the measurement of delays and simulation time while the time_precision specifies how delay values are rounded before being used in simulation. Use the following timescale constructs to use different time units in the same design.
What is $random in Verilog?
$random function call returns a 32-bit random number each time it is called. The random number is a signed integer; it can be positive or negative. Therefore, if 2-bit random varialbe is desired, you need a modulo operation as follows.
How do you get timescale in SystemVerilog?
In SystemVerilog, you can write (timevar = $time/1ns) or better (timevar $realtime/1ns) and you will get your time back in ns.
What is delay function?
Description. The Delay function models the Laplace expression e-sT, where T is the length of the delay in seconds and s is the Laplace operator. This is quite a simple function, which feeds the input into one end of an array table and as time advances, progresses to the end of the array.
What is delay in VLSI?
The RC delay model is a metric used in VLSI design to calculate the signal delay between the input voltage and output voltage of the input signal. The input signal is a step function. In this case the transistor can be considered as a switch in series with a resistor.
Why time is 4-state data types?
The time datatype is 4-state because Verilog only had 4-state integers. In Verilog, time and integer were similar types except that their size were platform dependent. SystemVerilog fixed time as a 64-bit unsigned integer, and integer as 32-bits.
What are 4-state data types?
Verilog’s variable types are four-state: each bit is 0,1,X or Z.
Integer and Real Types.
|byte||8 bits, signed||byte a, b;|
|shortint||16 bits, signed||shortint c, d;|
|int||32 bits, signed||int i,j;|
What is seed in Verilog?
Verilog has only one Random number generator. Random stimulus is generated using $random(seed) where the seed is input to the RNG. $random will always return the same value for same seed.
How do you repeat in Verilog?
A repeat loop in Verilog will repeat a block of code some defined number of times. It is very similar to a for loop, except that a repeat loop’s index can never be used inside the loop. Repeat loops just blindly run the code as many times as you specify.
What is a delay loop?
Time delay loops are often used in programs. These are loops that have no other function than to kill time. Delay loops can be created by specifying an empty target statement.
What does delay 1000 means?
This number represents the time in milliseconds the program has to wait until moving on to the next line of code. When you do delay(1000) your Arduino stops on that line for 1 second.
What is rise time in VLSI?
Rise time (tr) is the time, during transition, when output switches from 10% to 90% of the maximum value. Fall time (tf) is the time, during transition, when output switches from 90% to 10% of the maximum value. Many designs could also prefer 30% to 70% for rise time and 70% to 30% for fall time.
What is the data type of time?
Date and time data types
|time||hh:mm:ss[.nnnnnnn]||00:00:00.0000000 through 23:59:59.9999999|
|date||YYYY-MM-DD||0001-01-01 through 9999-12-31|
|smalldatetime||YYYY-MM-DD hh:mm:ss||1900-01-01 through 2079-06-06|
|datetime||YYYY-MM-DD hh:mm:ss[.nnn]||1753-01-01 through 9999-12-31|
What are Verilog data types?
In Verilog, data types are divided into NETS and Registers.
Integer and Real Data Types.
|byte||8 bits, signed|
|shortint||16 bits, signed|
|int||32 bits, signed|
|longint||64 bits, signed|
What is logic in Verilog?
SystemVerilog introduces a new 4-state data type called logic that can be driven in both procedural blocks and continuous assign statements. But, a signal with more than one driver needs to be declared a net-type such as wire so that SystemVerilog can resolve the final value.
What is bit in Verilog?
Integer and Real Types
Verilog’s variable types are four-state: each bit is 0,1,X or Z. SystemVerilog introduces new two-state data types, where each bit is 0 or 1 only. You would use these when you do not need X and Z values, for example in test benches and as for-loop variables.