Introduction to VLSI Design – Lec01. Chapter 1 Introduction to VLSI Design Lecture # 11 High Desecration Language- Based Design

Introduction to VLSI Design – Lec01. HDL-Based Design 1980’s: 1980’s: Hardware Description Languages (HDL) were conceived to facilitate the information exchange between design groups. 1990’s The increasing computation power led to the introduction of logic synthesizers that can translate the description in HDL into a synthesized gate-level net-list of the design. 2000’s: 2000’s: Modern synthesis algorithms can optimize a digital design and explore different alternatives to identify the design that best meets the requirements.

Introduction to VLSI Design – Lec01. Modeling Digital Systems VHDL is for writing models of a system Reasons for modeling –requirements specification –documentation –testing using simulation –formal verification –synthesis Goal –most reliable design process, with minimum cost and time –avoid design errors!

Introduction to VLSI Design – Lec01. HDL-Based Design

Introduction to VLSI Design – Lec01. Verilog Other than VHDL there are many hardware description languages available in the market for the digital designers such as Verilog, ABEL, PALASM, CUPL, and etc VHDL and Verilog are the most widely used HDLs. The major difference between hardware description programming languages and others is the integration of time. Timing specifications are used to incorporate propagation delays present in the system.

Introduction to VLSI Design – Lec01. Types of Representation: VHDL representation can be seen as text file describing a digital system. The digital system can be represented in different forms such as a behavioral model or a structural model. Most commonly known as levels of abstraction, these levels help the designer to develop complex systems efficiently.

Introduction to VLSI Design – Lec01. VHDL Programming Structure: Entity and Architecture are the two main basic programming structures in VHDL. Entity: Entity can be seen as the black box view of the system. We define the inputs and outputs of the system which we need to interface. Entity ANDGATE is Port (A: in std_logic; B: in std_logic; Y: out std_logic); End entity ANDGATE; Architecture: Architecture defines what is in our black box that we described using ENTITY. We can use either behavioral or structural models to describe our system in the architecture. In Architecture we will have interconnections, processes, components, etc.

Introduction to VLSI Design – Lec01. Architecture AND1 of ANDGATE is --declarations Begin --statements Y <= A AND B; End architecture AND1; Example entity andgate is port (A,B:in std_logic; C:out std_logic); end andgate; architecture b of andgate is begin --and is a basic VHDL operation. <= represents the signal assignment C<=A and B; end b;

Introduction to VLSI Design – Lec01. Basic VHDL Concepts Interfaces Behavior Structure Test Benches Analysis, elaboration, simulation Synthesis

Introduction to VLSI Design – Lec01. Modeling Interfaces Entity declaration –describes the input/output ports of a module entity reg4 is port ( d0, d1, d2, d3, en, clk : in bit; q0, q1, q2, q3 : out bit ); end entity reg4; entity nameport namesport mode (direction) port typereserved words punctuation

Introduction to VLSI Design – Lec01. VHDL-87 Omit entity at end of entity declaration entity reg4 is port ( d0, d1, d2, d3, en, clk : in bit; q0, q1, q2, q3 : out bit ); end reg4;

Introduction to VLSI Design – Lec01.

Modeling Behavior Architecture body –describes an implementation of an entity –may be several per entity Behavioral architecture –describes the algorithm performed by the module –contains process statements, each containing sequential statements, including signal assignment statements and wait statements

Introduction to VLSI Design – Lec01. Modeling Behavior

Introduction to VLSI Design – Lec01.

Modeling Structure Structural architecture –implements the module as a composition of subsystems –contains signal declarations, for internal interconnections –the entity ports are also treated as signals component instances –instances of previously declared entity/architecture pairs port maps in component instances –connect signals to component ports wait statements

Introduction to VLSI Design – Lec01.

VHDL-87 Can’t directly instantiate entity/architecture pair Instead –include component declarations in structural architecture body templates for entity declarations –instantiate components –write a configuration declaration binds entity/architecture pair to each instantiated component

Introduction to VLSI Design – Lec01.