RTL Verilog

RTL Verilog is a hardware description language used for designing digital circuits at the register transfer level. The term "RTL" stands for Register Transfer Level, which refers to the digital circuitry level that is defined by the flow of data between registers.

Features of RTL Verilog

• It is a high-level language used for designing complex digital circuits.
• It is a hardware description language used for synthesizing digital circuits.
• It supports simulation and verification of digital circuits.
• It is a powerful language that enables fast design iterations.

Basic syntax

The basic syntax of an RTL Verilog module is as follows:

module module_name(input input_signal_1, input input_signal_2, output output_signal);
  // Module code goes here
endmodule

Here, module_name is the name of the module, input_signal_1 and input_signal_2 are the names of the input signals, and output_signal is the name of the output signal.

Data types

RTL Verilog supports various data types that include:

• wire: It is used for connecting signals to the ports of a module. It is an output-only signal and cannot be used for storing values.
• reg: It is used for storing values within a module. It can be used for both input and output signals.
• integer: It is used for storing integer values.
• real: It is used for storing floating-point values.

Examples

Full adder

The following code implements a full adder using RTL Verilog:

module full_adder(input a, input b, input cin, output sum, output cout);
  assign sum = a ^ b ^ cin;
  assign cout = (a & b) | (cin & (a ^ b));
endmodule

Here, a, b, and cin are the input signals, sum and cout are the output signals. The ^ operator performs bitwise XOR and the & operator performs bitwise AND.

4-bit adder

The following code implements a 4-bit adder using RTL Verilog:

module four_bit_adder(input [3:0] a, input [3:0] b, output [3:0] sum);
  wire c0, c1, c2;
  full_adder fa0(a[0], b[0], 1'b0, sum[0], c0);
  full_adder fa1(a[1], b[1], c0, sum[1], c1);
  full_adder fa2(a[2], b[2], c1, sum[2], c2);
  full_adder fa3(a[3], b[3], c2, sum[3], 1'b0);
endmodule

Here, a and b are the input signals of size 4-bits, sum is the output signal of size 4-bits. The full_adder module is instantiated four times to perform addition of each bit. The wire data type is used for connecting the carries between the full adders.