This is a Verilog code that implements a 3to8 Decoder module and a testbench to verify its functionality.
-
Let's explain the code in detail:
-
The Decoder2x4 Module: The Decoder2x4 module represents a 2x4 decoder. It has three inputs (x, y, E) and four outputs (D0, D1, D2, D3). Each output represents one of the four possible combinations of the binary inputs.
__________________________________________________________________________________ | | | - Inputs: | | ---> `x`: Binary input signal. | | ---> `y`: Binary input signal. | | ---> `E`: Enable input signal. | | | | - Outputs: | | ---> `D0`: Output signal for binary input `00`. | | ---> `D1`: Output signal for binary input `01`. | | ---> `D2`: Output signal for binary input `10`. | | ---> `D3`: Output signal for binary input `11`. | | | | - Internal Signals: | | ---> `nx`: Complement of `x`. | | ---> `ny`: Complement of `y`. | | ---> `nE`: Complement of `E`. | | | | - Assignments: | | ---> `nx`, `ny`, `nE`: Assignments of the complement | | values for the inputs. | | ---> `D0`, `D1`, `D2`, `D3`: Assignments of the output signals | | based on the input combinations using logical AND gate operations. | |_________________________________________________________________________________| -
The Module Decoder3x8: The Decoder3x8 module represents a 3x8 decoder. It has three inputs (x, y, z) and eight outputs (D[7] to D[0]). Each output represents one of the eight possible combinations of the binary inputs.
__________________________________________________________________________________ | | | - Inputs: | | ---> `x`: Binary input signal. | | ---> `y`: Binary input signal. | | ---> `z`: Binary input signal. | | | | - Outputs: | | ---> `D[7:0]`: Eight-bit output signal representing the eight | | possible combinations of the binary inputs. | | | | - Internal Signals: | | ---> `D0`, `D1`, `D2`, `D3`: Four-bit output signals from two | | 2x4 decoder modules (`Decoder2x4`) used as sub-modules. | | | | - Assignments: | | ---> Instantiation of two `Decoder2x4` modules (`u1` and `u2`) and | | connections to the inputs and outputs. | | ---> `D`: Assignment of the eight-bit output signal by | | concatenating the four-bit output signals. | | (`D3[0]`, `D2[0]`, `D1[0]`, `D0[0]`, `D3[1]`, `D2[1]`, `D1[1]`, `D0[1]`) | | in the specified order. | |_________________________________________________________________________________| -
The Module Decoder3x8_tb: The Decoder3x8_tb module serves as a testbench for the Decoder3x8 module to verify its functionality. It instantiates the Decoder3x8 module (dut instance) and connects the input and output ports.
__________________________________________________________________________________ | | | - Inputs: | | ---> `x`, `y`, `z`: Testbench inputs representing the binary input | | values for `x`, `y`, and `z`, respectively. | | | | - Outputs: | | ---> `D`: Testbench output representing the expected eight-bit output | | signal (`D[7:0]`) from the `Decoder3x8` module. | | | | - Initial Block: | | ---> The `initial` block is responsible for test scenario execution | | and displaying the values of inputs and outputs using the | | `$display` and `$monitor` macros. | |_________________________________________________________________________________| | | | The following are the test scenarios executed: | | ---> 1. Set `x`, `y`, `z` to `0`. | | ---> 2. Wait for 10 time units. | | ---> 3. Set `x`, `y`, `z` to `0`, `0`, `1` respectively. | | ---> 4. Wait for 10 time units. | | ---> 5. Set `x`, `y`, `z` to `0`, `1`, `0` respectively. | | ---> 6. Wait for 10 time units. | | ---> 7. Set `x`, `y`, `z` to `0`, `1`, `1` respectively. | | ---> 8. Wait for 10 time units. | | ---> 9. Set `x`, `y`, `z` to `1`, `0`, `0` respectively. | | ---> 10. Wait for 10 time units. | | ---> 11. Set `x`, `y`, `z` to `1`, `0`, `1` respectively. | | ---> 12. Wait for 10 time units. | | ---> 13. Set `x`, `y`, `z` to `1`, `1`, `0` respectively. | | ---> 14. Wait for 10 time units. | | ---> 15. Set `x`, `y`, `z` to `1`, `1`, `1` respectively. | | ---> 16. Wait for 10 time units. | |_________________________________________________________________________________|
