Studio Session 1: Introduction to VHDL and related Tools EE19D – 25/01/2005

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Studio Session 1: Introduction to VHDL and related Tools

EE19D – 25/01/2005

Topic

Definitions Visual Introduction of VHDL using EVITA (

www.aldec.com) Getting started with Xilinx ISE Tool Simulation of VHDL Models with Moldelsim

Definition of an HDL

Def: A high level programming language used to model hardware.– special hardware related constructs– digital (now) and analog (near future)– models used for documentation, simulation,

synthesis, and test generation– have been extended to the system design level

Language Semantics

Semantics: what is the meaning of a language construct? HDLs have different semantics for different applications:

– Simulation– Synthesis– Test

In this course we will be concerned with simulation and synthesis semantics.

VHDL VHDL = VHSIC Hardware Description Language VHSIC = Very High Speed Integrated Circuit Program DOD began development in 1983

– design exchange among VHSIC contractors– document parts with long functional life

IEEE Standardization– Standardization process began in 1985– IEEE Standard 1076 in 1987– Updated in 1993

Significance of VHDL

VHDL provides a text based approach to structured hardware modeling and design.

Analogous to high level software languages such as PASCAL, C, C++, and JAVA.

An important tool in managing the complexity of VLSI systems.

Why Use VHDL?

Reason #1: it allows textual design representation

Reason #2: Ability to model at different levels of abstraction

Abstraction Levels

SYSTEM

CHIP

REGISTER

GATE

CIRCUIT

SILICON

SILICON LEVEL

CIRCUIT LEVEL

N

D

P

SV+

G

Vin Vout

DG

S Inverter

GATE LEVEL

S

Q

Q

R

Q

QR

S

Flip Flop

REGISTER LEVEL

Select

REG

REG

INC

MUX

CLK B

CLK A

CHIP LEVEL

µ

88

8

RAM

Par.Port

USART

Int.Con.

P

SYSTEM LEVEL

A/BComputer

IMU

C/D

RADAR

– VHDL Provides total modeling capability at the gate level, register level, and chip level.

– It can also be used in many applications at the: system level circuit level Switch level (gate-circuit hybrid)

VHDL supports very naturally the Design Decomposition process.

Structural

Decomposition

behavioralmodel

Reason #3: Design Decomposition

•VHDL can be used to validate design at a high level, thus detecting errors early in the design process

•Important, because finding errors later is expensive

Reason #4: Design Validation

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