Fpga ld 6j2l2h

LD (Complex Programmable Logic Device) • Need of LD : 

Due to limitations of SPLDs(PLA and PAL).

 It is Collection of PLDs and interconnection on same die.  Logic gates upto 10000 gates.  Vendors: Altera, Atmel, Cypress, Philips etc.

Structural Block Diagram of LD



Programmablen I/O blocks

PLD

PLD

PLD

Programmable Interconnect PLD

PLD

PLD

Detail Architecture of LD

Functional Block

Macrocell

Macrocell:  Consists:  AND-OR configuration(5-20 AND gates, OR gates with    

5-20 inputs). Ex-OR gate(provides inverted or noninverted output of ORgate). D-Flip-Flop. Multiplexer. Buffer.

Advantages of LD? • Ease of Design: With use of HDL & LD development tools • Reduced Board Area: As uses VLSI & available in tiny sizes. • Cost of Ownership: Due to less maintenance. • Lower Development Costs • More product revenue: Development cycles are very short & get into market quicker, generates revenue sooner. • Reliability

Field-Programmable Gate Arrays  Introduced in 1985 by XILINX Company.  Since then many different companies developed it: Actel, Altera, Algotronix,

Quick Logic, AMD, Cross Point Solutions etc.  PLAs: 100s of gate equivalents  FPGAs: 1000-few hundred 1000s gates  Logic blocks(CLB)  Implement combinational

and sequential logic

 Interconnect  Wires to connect inputs and

outputs to logic blocks

 I/O blocks  Special logic blocks at

periphery of device for external connections

CLB(Configurable Logic Blocks)  Number of ways defining CLB that it varies from simple

AND gate to very complex structure consisting MUX or LUT & so many PLA kind structure.

FPGA LOGIC BLOCK  4-input look up table (LUT)  Implements

combinational logic functions

  Optionally stores output

of LUT

 I/O pads configured as inputs  Selectable 2.5 V or 3.3 V

threshold levels  Optional pull-up resistor

 I/O pads configured as

outputs  Ability to drive LVTTL

and LVCMOS levels

Xilinx 4000 Interconnect

APPLICATIONS OF FPGA □Prototyping -Ensemble of gate arrays used to emulate a circuit to be manufactured -Get more/better/faster debugging done than with simulation □ Reconfigurable hardware -One hardware block used to implement more than one function □ Special-purpose computation engines -Hardware dedicated to solving one problem (or class of problems)

-Accelerators attached to general-purpose computers (e.g., in a cell phone!)

SEQUENTIAL PLD Output Logic Macrocell (OLM)

combinational config

product term

invert output?

ed config

D F/F

16

Difference between LD & FPGA Sr. No.

LD

1.

Complex Device

2.

It is collection PLDs.

It is collection of CLBs.

2.

Gate density up to 10000 gates

1000-few hundred 1000s gates

4.

Programmable

FPGA Logic Field Programmable Gate Array

Interconnection wise it is Programmable at field or site so called complex so called as LD. as FPGA.

5.

PAL like blocks used as PLDs.

CLBs used as building blocks.

6.

AND-OR arrays are there in PAL LUTs are there in CLBs. like blocks.

7.

Configuration context is stored in Configuration context is stored in ROM. RAM.

8.

Configuration context is Non- Configuration context is volatile. volatile.