Why output is reg in Verilog?

Why output is reg in Verilog?

5 Answers. reg and wire specify how the object will be assigned and are therefore only meaningful for outputs. If you plan to assign your output in sequential code,such as within an always block, declare it as a reg (which really is a misnomer for “variable” in Verilog).

Why is always used in Verilog?

Uses of always block An always block can be used to realize combinational or sequential elements. A sequential element like flip flop becomes active when it is provided with a clock and reset. Similarly, a combinational block becomes active when one of its input values change.

What is always (*) in Verilog?

The (*) means “build the sensitivity list for me”. For example, if you had a statement a = b + c; then you’d want a to change every time either b or c changes. In other words, a is “sensitive” to b & c . So to set this up: always @( b or c ) begin a = b + c; end.

How do you stop always in Verilog?

Verilog always block

1. always @ (event) [statement] always @ (event) begin [multiple statements] end.
2. // Execute always block whenever value of “a” or “b” change always @ (a or b) begin [statements] end.
3. // Execute always block at positive edge of signal “clk” always @ (posedge clk) begin [statements] end.

When is the always block triggered in Verilog?

The always block is triggered whenever any of the signals in the sensitivity list changes in value. Output signal is declared as type reg in the module port list because it is used in a procedural block. All signals used in a procedural block should be declared as type reg.

Why does Verilog always need a sensitivity list?

Note: Explicit delays are not synthesizable into logic gates ! Hence real Verilog design code always require a sensitivity list. The code shown below defines a module called tff that accepts a data input, clock and active-low reset. The output gets inverted whenever d is found to be 1 at the positive edge of clock.

When is the clock inversion done in Verilog?

Now, the clock inversion is done after every 10 time units. Note: Explicit delays are not synthesizable into logic gates ! Hence real Verilog design code always require a sensitivity list. The code shown below defines a module called tff that accepts a data input, clock and active-low reset.

What kind of logic can we model in Verilog?

As we discussed in the post on verilog operators, there are two main classes of digital circuit which we can model in verilog – combinational and sequential. In contrast to combinational logic, sequential circuits use a clock and require storage elements such as flip flops.