In the VLSI design pipeline, which entails building electronic circuits utilizing combined circuits (ICs), RTL design is an essential stage. It requires a digital circuit in terms of the logical operations. That carries out on the digital signals that go between hardware registers.
Here, the hardware designer uses a hardware description language (HDL) like Verilog or VHDL to explain the circuit’s performance. A gate-level netlist, or a representation of the circuit at the level of gates and connections. These descriptions combine to create it. In fact, with CAD software, you can lay out the circuit physically on an integrated circuit (IC).
Prior to the development of HDL, engineers created a circuit with full functionality by schematic entry. It is conceivable that designing a 32-bit adder would require designing all of the logic in gates. Which would have made the design process laborious and error-prone.
HDL design transformed this self-designing task into a simple automated process. Allowing the designer to write the functionality of the design in any language they choose. And having a tool to translate all of his designs into the corresponding combinational and/or sequential circuit.
Types of RTL Design
Combinational HDL Design
Combinational HDL design can be defined by circuits with no internal memory or state that carry out logical operations.
A digital circuit type known as a combinational circuit has an output that is solely dependent on the input.
Sequential HDL Design
Sequential HDL design is a type of circuit design that consists of a series of combinational circuits with internal memory or state.
The output of a sequential circuit is a form of digital circuit that depends on the previous order of inputs in addition to the current values of the input signals it possesses.
Combinational HDL Design vs Sequential Design
Digital circuit design employs two methodologies, each with unique features and uses: combinational HDL design and sequential HDL design.
The circuit’s output in a combinational HDL design is solely dependent on its current inputs. Combinational circuits lack feedback loops and internal memory components.
Combinational circuits are made to carry out certain tasks without requiring the storage of interim outcomes. A few instances of combinational circuits are logic gates, multiplexers, and adders.
Comparing combinational HDL designs to sequential designs, the former is usually faster and simpler to use.
However, Circuits designed with sequential HDL technology have an output that is dependent on both the system’s prior states and its present inputs.
Flip-flops and registers are examples of memory components used in these designs to store interim findings and preserve state data.
In other words, applications where the system needs to recall previous inputs or carry out actions based on a series of events frequently employ sequential circuits.
Sequential circuits include, for example, microprocessors, counters, and finite state machines.
As sequential HDL designs have memory components and feedback loops, they are more complicated than combinatorial designs and may operate more slowly.
HDL Design Gears
Synthesis Gear
The HDL code is fed into synthesis gear, which outputs a gate-level netlist.
Simulation Gear
Namely using simulation tools, we can test an RTL design by providing it with input stimuli and observing the resulting output responses to ensure it functions correctly.
Verification Gear
Additionally, model checking and theorem proving are used to ensure that the design is correct and comprehensive using formal verification techniques.
In Conclusion
To sum up, RTL design is a crucial phase in the VLSI design process that involves describing digital circuits in terms of the signals. Signals carrying out the move between hardware registers and the logical operations. In addition to taking temporal, power, and space limits into account, it entails the use of HDLs, synthesis, simulation, and verification tools. However, designers can produce effective and high-performing digital circuits for use in a variety of applications by employing a suitable RTL coding style and keeping these factors in mind.
In order to get a better understanding about what HDL design is it is better to first understand the concept of it. It will be easy to learn its use in the modern world.