7/28/2019 FPGAS 17-11-09

1/34

Introduction to programming

technologies

One of the first technique that allowed users to

program their own devices was- and still is

known as fusible-link technology.

In this case the device manufactured with all

of the links in place, where each link is

referred to as a fuse.

7/28/2019 FPGAS 17-11-09

2/34

Fusible Link technologies

A simple programmable function

Every Programmable function is implemented using

Potential links

Pull up resistors

Input and output terminals

7/28/2019 FPGAS 17-11-09

3/34

Un programmable fusible links

In Un programmable fusible links uses the fuses aresimilar to the fuses you find in household products like a

television. If anything untoward occurs such that the

television starts consuming too much power its fuse will

burn out.

This results in an open circuit

7/28/2019 FPGAS 17-11-09

4/34

Programmable Fusible Links

Here programming is done by selectively removing the

undesired fuses by applying pulses of relatively high voltage

and current to the devices inputs.

7/28/2019 FPGAS 17-11-09

5/34

The process of selectively removing the fuses is

known as programming( but it may also referred to as

burning or blowing)

7/28/2019 FPGAS 17-11-09

6/34

Drawback

Devices based on the fusible link technologies are

said to be one-time programmable(OTP), because

once a fuse have been blown it cant be and no going

back..

7/28/2019 FPGAS 17-11-09

7/34

Antifuse technology

This Antifuse technology is an alternative to the fusible technology

In which each configurable path has an associated link called Antifuse.

In its unprogrammmed state Antifuse has high resistance that is considered

to be an open circuit.

7/28/2019 FPGAS 17-11-09

8/34

Programming an antifuse

Antifuses can be selectively grown(programmed) by applying

proper high voltages and currents to the device's inputs

7/28/2019 FPGAS 17-11-09

9/34

The Polysilicon via converts insulation to conduction

7/28/2019 FPGAS 17-11-09

10/34

These antifuses are also OTP devices

7/28/2019 FPGAS 17-11-09

11/34

MASK PROGRAMMABLE DEVICES

Electronic systems in general and computers in particular-

make use of two major classes of memory devices: read-only

memory (ROM) and random-access memory(RAM)

ROM:

1.nonvolatile

.2.Other components in the system can read data from ROMdevices, but they cant write data into them.

RAM:1. Volatile

2.By comparison data can be both written into and read out ofRAM devices which are said to be volatile .

7/28/2019 FPGAS 17-11-09

12/34

Basic ROMs are mask programmed

Their construction by means of photo masking.

Photo masking is used to create transistors

and metal tracks

ROM

7/28/2019 FPGAS 17-11-09

13/34

7/28/2019 FPGAS 17-11-09

14/34

7/28/2019 FPGAS 17-11-09

15/34

The problems of Mask devices

Creating the masks are very expensive

They are useless, unless producing theextremely large quantities

To overcome the above problem theyinvented programmable ROMs

PROM, EPROM,EEP[ROM

7/28/2019 FPGAS 17-11-09

16/34

PROM

7/28/2019 FPGAS 17-11-09

17/34

Thses are used as memory devices

Used to implement simple logics

Cheap

They designed using fusible and anti

fusible technoilogies

7/28/2019 FPGAS 17-11-09

18/34

EPROM

Theses are also called as reprogrammable

devices

Being introduced by Intel in 1971

Its structure is same as standard MOS

transistor but with the addition of second

polysilicon floating gate isolated by layers

of oxide.

7/28/2019 FPGAS 17-11-09

19/34

7/28/2019 FPGAS 17-11-09

20/34

In its unprogrammed state , the floating

gate uncharged and doesnt affect the

normal operation of the control gate.

Inorder to program the transistor , a

relatively high voltage is applied b/w drain

and gate

7/28/2019 FPGAS 17-11-09

21/34

This 12V causes the transistor to be truned on

and energetic electrons force their way through

the oxide into the floating gate in a processknown as hot (high enery ) electronic injection.

When the programming signal is removed a

negative charge remains on the floating gate

and it is stable and will not dissipate more than

one decade under normal operations.

7/28/2019 FPGAS 17-11-09

22/34

7/28/2019 FPGAS 17-11-09

23/34

7/28/2019 FPGAS 17-11-09

24/34

An EPROM is erased by discharging the

electrons on that cells floating gate.

The energy required to discharge the electrons

by a source of ultraviolet (UV) radiation

If the area smaller amd then density increases, alarger percentage of the surface of the die is

covered by metal. This makes it difficult for the

EPROM cells to absorb the UV light and

increase the time.

7/28/2019 FPGAS 17-11-09

25/34

EEPROM

7/28/2019 FPGAS 17-11-09

26/34

The E2PROM transistor is same as

EPROMtransistor in that it contains a

floating gate , but the insulating oxide

layers surroung this gate are very muchthinner.

The second transistor used to erase the

data.

7/28/2019 FPGAS 17-11-09

27/34

FLASH based technologies

A deThe name FLASH was originally

coined to reflect this technologies rapid

erasure times compared to EPROM

It has two types of architectures .

7/28/2019 FPGAS 17-11-09

28/34

In the first architecture using a singlefloating gate transistor cell with the samearea as an EPRM and thinner oxide like

layer like EEPROM. SO theses devices can clearing large

portions of the data.

The other architecture uses two-transistorcell similar to EEPROM cell to erase wordby word,.

7/28/2019 FPGAS 17-11-09

29/34

SRAM based technology

RAMs are two types

SRAM and DRAM

DRAMs : In the case of DRAMs , each cell isformed from a transistor-capacitor pairthat

consumes very little silicon material .

The dynamic qualifier is used because thecapacitor loses its charge over time, so each cell

must be periodically rechraged periodically to

retain its data.

7/28/2019 FPGAS 17-11-09

30/34

The output of the SRAM IS CONTROLED BY A

CONTROL TRANSISTOR

7/28/2019 FPGAS 17-11-09

31/34

Dis Advantage:

1. It Uses significant amount of siliconbecause each cell comprises of four to six

transistors 2. When power is removed the configured

data will be lost.

Advantage: Thhey can be programmed quickly and

repeateadly as required.

7/28/2019 FPGAS 17-11-09

32/34

7/28/2019 FPGAS 17-11-09

33/34

7/28/2019 FPGAS 17-11-09

34/34