Intro many different types of logic devices. First,

                                             Intro to programmable logic/ Devices

       Programmable
logic devices are one of the electronic devices that used to build and
configure the

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Digital circuit. Compare to logic gate, this is undefined
function at the time of manufacture. First

Programmable logic was introduced at the time of 1969. It
was founded by Motorola, known as XC-157.

This is composed of 12gates and 30 uncommitted input or
outputs. After that, Texas instruments

made another new programmable logic that programmable IC.
This is based on IBM-read associative

with Memory or ROM. This device is known as the TMS 2000.
This device is composed of 17 inputs and

18 outputs with 8 JK flip flop for memory. In 1971, Company
knows as General Electric founded new

programmable logic device. This experimental device improved
on IBM’s ROAM with allowing multilevel

logic. In 1973 National Semiconductor introduced a PLA
device with 14 inputs and 8 outputs with no

memory registers.

      There are various
advantages that programmable logic devices have. First, There is no need for
the

time-consuming logic design of random-logic gate. This makes
program quicker than just wiring

bunch of electronic circuit with complex system. Second,
checking the design is easy, and change the

design is also easy. Third, Layout is far simpler than that
for random-logic gate. So, it is less time-

consuming. Fourth, PLA is a very inexpensive approach,
greatly shortening designing time. PLAs have the

following disadvantages compared with random-logic gate
networks.

    There are several
disadvantages of the programmable logic devices. First, for storing the same

function or tasks, PLAs can be smaller than ROMs. Second, Design
and the layout of random-logic gate

networks are far more tedious and time- consuming.

      Also, there are
many different types of logic devices. First, I want to talk about SPLD. This
is simplest,

and smallest, and not much expensive form of programmable
logic device. This is very similar to a

Complex form, but an SPLD will have less IO pins and programmable
components, consumes less

Power and requires special programming device to figure out.
This is non-volatile and remaining their

state after power is removed.  Microchip SPLD products consist of industry
standard 16V8 and 22V10s in

a variety of voltage. They typically composed of 4 to 22
fully connected macro-cells. These macro-cells

typically composed of some combinatorial logic like And /OR
gate. It used in boards to change the

standard basic logic of And/OR gate.

       Another unique
type of programming logic devices are known as the CPLD. It stands for complex

programmable logic device. It is device that have the architectural
features of both, PALS and FPGAs.

CPLD is composed of two features. Non-volatile memory, and
legacy CPLD devices. CPLD is an

evolutionary step from even smaller devices than PLAs.

     The main
distinction between FPGA and CPLD device architectures is that FPGAs are internally
based

on look-up tables. FPGA is stands for  field-programmable gate array. This is an
integrated circuit

designed to be configured by a customer or a designer after
manufacturing – hence “field-

programmable”. This is composed of array of
programmable logic blocks. Logic blocks exist  to perform

complex combinational functions, simply logic gates like AND/XOR.
This device trying to implement

complex digital computations. Examples are PAL known as programmable
array logic, General array

logic, Programmable logic array, programmable logic device.  Most important feature of SPLD is

macro-cell.Macro-cell is fully connected to the others in
the device. Some of SPLDs use either fuses or

non-volatile memory cells such as EPROM, EEPROM, or FLASH to
define the functionality. Most SPLD’s

are used within EPROM, EEPROM, or FLASH to define the
functionality.

   CPLD is compose of
the two to 64 SPLDs. CPLD composed of tens to a few hundred macro-cells.

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