Actel fpga

ACTEL FPGAs

Dr. D. V. Kamath

Professor, Department of E&C Engg.,

Manipal Institute of Technology, Manipal

1

2

FPGAs

FPGAs are pre-fabricated silicon devices that can be

electrically programmed to implement any digital system

Important characteristics of FPGAs (Field Programmable Logic

Devices) are as follows:

• Customized by end user

• Implements multi-level logic function

• Fast time to market and low risk

3

FPGAs

Advantages of FPGAs:

• Configuring a FPGA using a hardware description language

(HDL) is faster than developing an ASIC

• Easy design upgradation using FPGA due to its reconfigurability

• FPGAs are perfect choice for rapid prototyping of digital circuits

Disadvantages of FPGAs:

• FPGA needs more space (transistors) on chip as compared to the

ASIC counterpart for the same application

• The application runs slower on a FPGA when compared with its

ASIC counterpart

4

FPGAs and ASICs

ASIC FPGA

• Designs must be sent for

expensive and time consuming

fabrication in semiconductor

foundry

• FPGAs can be bought off the shelf

and reconfigured by designers

themselves

• Designed all the way from

behavioral description to physical

layout

• No physical layout design; design

ends with a bitstream used to

configure a device

• Low cost in high volumes

• Low development cost

• High performance

• Reconfigurability and short time to

market

5

FPGA architecture

An FPGA consists of a large number of configurable logic cells.

Each logic cell can be configured to implement a certain set of

function.

Each logic cell has a fixed number of inputs and outputs.

Basic building blocks in FPGA architecture are

• CLB Configurable logic block

• IOB Input/ Output block

• Interconnect : connection between CLBs and between CLBs

and IOBs

6

FPGA

General structure of an FPGA

7

FPGAs

Two types of FPGAs Reprogrammable FPGA Uses memory based logic cells Uses sRAM configuration cell

Vendors : Xilinx , Lattice, Atmel, Altera One-time Programmable(OTP) FPGA Uses multiplexer based logic cells Antifuse switch based

Vendors : Actel, Quicklogic Xilinx Inc. and Altera Corp. share 60% of the FPGA market.

8

2-input MUX as programmable logic block

F

A 0

B

S

1

Configuration

A B S F=

0 0 0 0

0 X 1 X

0 Y 1 Y

0 Y X XY

X 0 Y

Y 0 X

Y 1 X X + Y

1 0 X

1 0 Y

1 1 1 1

XY

XY

X

Y

9

Multiplexer logic as function generator

Shannon’s Expansion Theorem

Let a function F(a, b, c) is expanded with respect to a, then F can be expressed as

𝐹 = 𝑎 . 𝐹𝑎+𝑎 . 𝐹𝑎

where 𝐹𝑎 = F/a = 1 and 𝐹𝑎 = F/a = 0

Implementation of two-level combinational function using multiplexers

10

Multiplexer logic as function generator

Shannon’s Expansion Theorem

The function can be recursively or simultaneously expanded with respect to two or three variables.

𝐹 = 𝑎 . 𝑏 . 𝐹𝑎 𝑏 +𝑎 . 𝑏 . 𝐹𝑎 𝑏 + a. 𝑏 . 𝐹𝑎𝑏 + a.b . 𝐹𝑎𝑏

Implementation of multi-level combinational function using muxs

11

ACTEL FPGAs

ACTEL FPGA uses multiplexer based logic cells

The multiplexer-based logic module is typically composed of a

tree of 2-to-1 MUXes.

Different types of Logic Modules(LMs) available are :

ACT 1 LM

ACT 2 - C, ACT 2 - S

ACT 3 - C, ACT 3 - S

12

ACTEL FPGAs

ACTEL ACT1 Logic module (LM)

13

ACT 1 Logic Module (LM)

Implementation of combinational function using ACT1 Logic Module (LM)

14

ACT-2 C-Module

ACTEL ACT2 Combinational Logic module (LM)

15

ACT 2 S-Module

ACT2 Sequential Logic module (LM)

16

ACT 3 S-Module

ACT3 Sequential Logic module (LM)

17

ACT 2 S-Module

Internal circuit of SE(sequential element)

18

SE can be configured as a positive edge triggered D flip-flop by Selecting 𝐶1 = 0 and 𝐶2 = CLK

19

ACT 2 S-Module

SE configured as a positive edge triggered D flip-flop

20

• [email protected]

• [email protected]

Contact