Pruthvi-Sanghavi / learning-verilog-in-a-day

A one day streak at learning verilog

learning-verilog-in-a-day

A one day streak at learning verilog

Introduction

Verilog is used to simulate the logic gates in realtime without using any hardware. It also provides functionalities to visualize the signals.
Verilog is a HDL (Hardware Description knowledge). It is a language used for describing a digital system like a network switch or a microprocessor or a memory or a flip−flop. It means, by using a HDL we can describe any digital hardware at any level. Designs, which are described in HDL are independent of technology, very easy for designing and debugging, and are normally more useful than schematics, particularly for large circuits.

Verilog is used to write digital logic.

Register Transfer Level

In digital circuit design, register-transfer level (RTL) is a design abstraction which models a synchronous digital circuit in terms of the flow of digital signals (data) between hardware registers, and the logical operations performed on those signals.

Register-transfer-level abstraction is used in hardware description languages (HDLs) like Verilog and VHDL to create high-level representations of a circuit, from which lower-level representations and ultimately actual wiring can be derived. Design at the RTL level is typical practice in modern digital design.

Logic and Test Bench

In Verilog we can divide the program into two files:

1. Design Under Test (DUT): A DUT verilog file which contains only the logic.
2. Test Bench (TB): A testbench file which contains the values assigned to the original variables and is used for testing.

Abstractions of the verilog HDL

Gate level Modelling (Lower level of Abstraction)

• Verilog supports coding circuits using basic logic gates as predefined primitives. These primitives are instantiated like modules except that they are predefined in Verilog and do not need a module definition.

Data Flow Modelling (Middle level of Abstraction)

• Dataflow modeling is a very important way of implementing the design. All you need to know is the boolean logic equation of the output of the circuit in terms of its inputs. We use continuous assignments in dataflow modeling in most of the designs. The continuous assignments are made using the keyword assign.

Behavioral Modelling (Highest level of Abstraction)

• Behavioral modeling is the highest level of abstraction in the Verilog HDL. All that a designer need is the algorithm of the design, which is the basic information for any design. This level simulates the behavior of the circuits; the details are not specified. That’s helpful because the designer does not have to deal with complicated circuitry or equations. Just a simple truth table would suffice.

Installing the compiler

sudo apt install iverilog

• I am using gedit as a text editor.

Installing the Simulator

sudo apt install gtkwave

First Program - Hello World!

• Compile as follows iverilog -o helloworld helloworld.v
• Run as follows vvp helloworld

Second Program - Positive Edge Detector

• Compile as iverilog -o ped posEdgeDetector.v
• Run as vvp ped

Third Program - Counter

• Compile as iverilog -o counter counter_tb.c counter.v
• Run as vvp counter
• Simulate - gtkwave test.vcd &

Fourth Program - The AND Gate

Compile - iverilog -o and_bm and_bm.v and_bm_tb.v
Run - vvp and_bm
Simulate - gtkwave dump.vcd &

Fifth Program - The D Flipflop

A D flipflop is used in FPGA to keep the history or the past states.

The main elements of D Flipflop are

1. D --> Data (Input)
2. > --> Clock (Input): clock is a square wave function repeating at some specific frequency. The unit is cycle per second or hertz.
3. Q --> Output

Reflection

I think I actually sort of missed the point of learning verilog.

References

1. https://www.chipverify.com/verilog/verilog-tutorial
2. https://www.nandland.com/verilog/tutorials/tutorial-introduction-to-verilog-for-beginners.html
3. https://technobyte.org/verilog-course-tutorials/
4. https://numato.com/kb/learning-fpga-verilog-beginners-guide-part-1-introduction/