Verilog Basics

2 minute read


Verilog was used to resolve the complexity of handling gate-level representation. This was first released as a proprietary language in 1985, and later it becomes publically available under IEEE standards.

These are simple examples I have done during the practical Session for Hardware Description Language Module

  1. Sequence/Pattern Detector. This was a simple example used to detect the pattern 1101 using the Mealy method. The mealy method has fewer states than the Moore model. For this, we have for the state using the Mealy Model. S1 = Reset state which comes at initial and in case of the wrong pattern matches like 10, 1100. S2 = the Second state which comes after the initial step with only 1; it has also come after the S4. S3 = Third state which comes only after the S2 and S3 itself thus when 111 once it will interpret again as 11. S4 = Last state which only comes after S3.

  2. D Flip Flops This was a simple d flip flops. Using the following methods.
    1. Synchronous Reset
    2. Asynchronous Reset
    3. If/Wait Statement
  3. Shift Register This was to shift register values based on the inputs. This particular register will shift the bits 4 clock cycles. Thus a particular input reaches after 4 clock cycles and also with asynchronous reset.

  4. Frequency Divider Here I divide the main clock frequency by 3(2'b010), thus after every 6 clock cycle, one pulse will come from the new clock. For this, I have used a counter which counts 0 to 2 and after that toggle clock value.

  5. ALU This was a simple ALU that contains a set of 16 operations with +, -, AND, OR, NAND, NOR, XOR, XNOR, and NOT gate. This divided into sub-modules as
    1. Arithmetic Unit ( operation with +, -)
    2. Logic Unit ( operation with AND, OR, NAND, NOR, XOR, XNOR, and NOT gates )
    3. Mux ( to choose Arithmetic or logic based on the operation selection )
  6. Sample Process This was a simple process designed with the help of the following units
    1. Alu unit (for both Arithmetic and logical calculation)
    2. Shift unit (shifting values)
    3. Register (storing values)
    4. Mux (toggle between values)
  7. Counter This was a simple example of down-counter counts from 8 till 3 and notify 1 when it becomes 5. This works with a clock, a load 8 function, which updates the counter values to eight and an enable function with common general meaning. Instead of previous examples, I have used a new approach based on what I learned recently. It contains three modules
    1. For main counter operation
    2. For testing purposes thus inputs and outputs of the original counter are reverted here
    3. For test bench to make the connection between test and counter

This was a quite initiative way to provide some examples of Verilog and give some basic understanding. This is strictly for beginners. Checkout my Github Repo on Verilog Examples.