In this case, the text message displayed onto the screen is 'Hello World !'. Its primarily used to help with testbench and design debug. $display is a Verilog system task used to display a formatted string to the console and cannot be synthesized into hardware. The initial block starts and executes the first statement at time 0 units. For our purposes, we'll simply display 'Hello World'Ī module called tb with no input-output ports act as the top module for the simulation. Verilog supports displaying signal values to the screen so that designers can debug whats wrong with their circuit Initial block is another construct typically used to initialize signal nets and variables for simulation Verilog code is always written inside modules, and each module represents a digital block with some functionality Single line comments start with double forward slash '//'

It's always best to get started using a very simple example, and none serves the purpose best other than 'Hello World !'. If reset is 1, then design should be allowed to count up, so increment counter Once inside this block, it checks if the reset is 0, if yes then change out to zero This always block will be triggered at the rising edge of clk (0->1) Output reg out) // Declare 4-bit output port to get the counter values Input rstn, // Declare input port for reset to allow the counter to be reset to 0 when required Module counter ( input clk, // Declare input port for clock to allow counter to count up There is a 4-bit output called out which essentially provides the counter values. An active-low reset is one where the design is reset when the value of the reset pin is 0. The design contains two inputs one for the clock and another for an active-low reset. When counter is at a maximum value of 4'b1111 and gets one more count request, the counter tries to reach 5'b10000 but since it can support only 4-bits, the MSB will be discarded resulting in 0. The rollover happens when the most significant bit of the final addition gets discarded. It will keep counting as long as it is provided with a running clock and reset is held high. The 4-bit counter starts incrementing from 4'b0000 to 4'h1111 and then rolls over back to 4'b0000.

Fifo verilog code basic