Assic 5th Lecture
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This document discusses different levels of abstraction in Verilog HDL modeling including switch level, gate level, register transfer level (RTL), and behavioral level. It describes modeling techniques like switch-level modeling, gate-level modeling, dataflow modeling, and behavioral modeling. The document also covers key concepts in Verilog like modules, module components, module ports, port assignments, hierarchical design, and module instances. Modules are the basic building blocks in Verilog and allow designers to mix abstraction levels and hierarchically interconnect components.
Assic 5th Lecture
- 1. 1 Verilog HDLVerilog HDL ASIC DESIGN USING FPGA BEIT VII KICSIT Sep 4 2012 Lecture 5
- 2. 2 Abstraction Levels Sep 4 2012 • There are four levels of abstraction • Switch level • Gate level • RTL (Dataflow) level • Behavioral or algorithmic level Lecture 5
- 3. 3 Modeling Techniques Sep 4 2012 • Switch-Level Modeling The lowest level of abstraction is the switch or transistor Level Modeling. (It is rarely used) • Gate Level Modeling It is feasible for small circuits. Lecture 5
- 4. 4 Modeling Techniques Sep 4 2012 • Dataflow Modeling The level of abstraction higher than the gate level. • Behavioral Modeling In more complex digital designs, priority is given to the performance and behavior of the algorithm. Lecture 5
- 5. 5 Modeling Techniques Sep 4 2012 • Verilog allows the designer to mix and match all four levels of abstractions in a design. • In the digital design community, the term register transfer level (RTL) is frequently used for a Verilog description that uses a combination of behavioral and dataflow constructs and is acceptable to logic synthesis tools. Lecture 5
- 6. 6 Modeling Techniques Sep 4 2012 • Normally, the higher the level of abstraction, the more flexible and technology-independent the design. • As one goes lower toward switch-level design, the design becomes technology-dependent and inflexible. • A small modification can cause a significant number of changes in the design in Low level abstration. Lecture 5
- 7. 7 Module Sep 4 2012 • The Module Concept • The module is the basic building block in Verilog • Modules are: • Declared • Instantiated • Modules declarations cannot be nested Lecture 5
- 8. 8 Module Sep 4 2012 • Modules can be interconnected to describe the structure of your digital system • Modules start with keyword module and end with keyword endmodule • Modules have ports for interconnection with other modules Lecture 5
- 9. 9 Module Sep 4 2012 •Everything you write in Verilog must be inside a module exception: compiler directives Lecture 5
- 10. 10 Module Sep 4 2012 Lecture 5
- 11. 11 Components of a Verilog Module Sep 4 2012 Lecture 5
- 12. 12 Components of a Verilog Module Sep 4 2012 Lecture 5
- 13. 13 Components of a Verilog Module Sep 4 2012 Lecture 5 • Stimulus and Design blocks can also be instantiated in a Dummy Top level module
- 14. 14 Module Ports Sep 4 2012 • Similar to pins on a chip • Provide a way to communicate with outside world. • Ports can be input, output or inout Lecture 5
- 15. 15 Port Assignments Sep 4 2012 Lecture 5
- 16. 16 Hierarchical Design Sep 4 2012 Lecture 5
- 17. 17 Module Instances Sep 4 2012 • Verilog design models consist of a hierarchy of module instances. • Like in C++ : modules are classes and instances are objects. • The process of creating objects from a module template is called instantiation. Lecture 5
- 18. 18 Module Instances Sep 4 2012 • As an example a top-level block ripple_crry_counter creates four instances from the T-flipflop (T_FF) template. • Each T_FF instantiates a D_FF and an inverter gate. • Each instance must be given a unique name. Lecture 5
- 19. 19 Module Instances Sep 4 2012 Lecture 5