Programmable logic devices are one of many electronic
devices that used to build and configure the
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 electronic 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
There are various
advantages that programmable logic devices have. First, There is no need for
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
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
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.
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.
distinction between FPGA and CPLD device architectures is that FPGAs are internally
on look-up tables. FPGA is stands for the 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
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
CPLD is compose of
the two to 64 SPLDs. CPLD composed of tens to a few hundred macro-cells.
CPLD is just multiple PAL- logic blocks with 4 to 16
macro-cells. Field Programmable Gate
Logic Cell Array,
programmable ASIC, FLEX, APEX, ACT, ORCA, Vertex, Quick logic. Those are came
each different company. This is distinct from SPLD and
Logic Controller have features are sequential control, counters and timers,
ease of programming, reliable controlling capabilities. PLC is using for washing machine, elevator,
signal. Programmable logic have multiple modules. Such as CPU
module, Power supply module, I/O
module, PLC Architecture. Each module have various different
First, CPU module
is just central processor that performing computation, processing data by
input and output.
Second, Power supply module is supply the power to the whole system by
AC power to DC power for CPU and I/O module. I/O module is
input and output module of the PLC for
between sensor and actuator. Sensors are such as measuring the temperature,
and flows. There are two type of I/O modules are digital and
analog. Another type is Communication
Interface Module. This transfers the information between a
CPU and communication network. Central
processing Unit of programmable logic controller consists of
operating system and user programs.
There are some of
steps of the running for PLC Scan cycle. First, Operating system starts cycling
monitoring. The CPU starts to read the data from input
module and checks status of all inputs. The
CPU executing the application program written in
relay-ladder logic/ PLC programming language. Then,
CPU performs communication tasks. And data goes through the output modules and
automatically automated. Pressure switch, temperature switch
are input field devices. And manual push
buttons are hardwired to an input module.
The glass industry
run by the Programmable logic devices. During the 1980s, Programmable logic
controls widely used to assembling of workshop of the glass
industry. While the increasing the demand
of Programmable logic, PLC became known as intelligent
device for the glass industry. Glass industry is
a type of the distributed control system attribute with
Programmable logic device.
control also used in Cement industry. DCS with bus technology is used in the
production of the cement industry. The PLC is in user mode
of SCADA. SCADA mode configuring the PLC
and main computer that control the programmable logic
control. The main computer have 2
which knowns as the Slave and master station. The most common function of Programmable logic
device is actually industrial automation.
Their programming language is sequence of
binary number of machine code. This is used to translate
mnemonics into the code of machine. Those devices using
specific symbols known as the ladder logic.
Ladder logic is the schematic of the relay circuit diagrams.
This is the diagram that composed of two
Vertical lines representing the power rails, horizontal
lines between two verticals are representation of
the relay ladder logic circuit.
Ladder logics have
their own unique features. First, Power flows from left to right. Second, Output
right side cannot be connected directly with left side. Third,
Contact cannot be placed on the right of
output. Fourth, Each rung contains one output at least.
Fifth, each output can be used only once in the
program. Sixth, a particular input a/o output can appear in
more than one rung of a ladder.
Seventh, the inputs a/o outputs are all identified by their
addresses, the notation used depending on the
symbols of the programmable logic is instructions. There are many kinds of the
Symbol like Examine if closed, which is normally open. Examine
if closed, which is normally closed.
OTE, which is Output Enable. The instruction is the action of
the conventional relay coil. TON, which is
stands for the timer ON. If enabled until set-point is
reached then the timer output goes true, and stays
true until the input (enable) line goes false. Off Timer,
which is stands for TOF. OFF timers begin timing
on a true-to-false transition, and continue timing as long
as the preceding logic remains false. When the
time equals the set-point the Time-OFF, output goes on, and
stays on until the rung goes true. RTO
stands for the retentive timer ON. This does not reset the time
when the input condition goes false.
There are two types of the latching relays. Output latch and
Output Unlatch are stands for OTL, and
OTU. If the unlatch instruction is true then the relay
output is false. Latch and unlatch relays are
separate operators. JSR is Jump to subroutine. This is for
the umping from one rung.
There is also
international standard of the logic controller. This is known as the IEC 61131.
first independent standardized programming language for
industrial automation. Demand is driven by
the increasing software complexity of control and automation
requirements. Labor cost, and
cost of control software has a major cause of the developing
of the international Programmable logic
control. This device combined
with revolutionary architectures to be able to control an entire controller
to be delivered in an embedded system.
This enables to transport
automation with the solutions to other platforms improved over PLC
Applications. IEC have unique elements. Such as Data Typing,
Configuration, Resources, and Tasks,
Program Organizations Units, unique type of programing
languages, and Co-De-Sys.
This is one of
the example of the code of the IEC.
FOR I:=1 TO 16 BY 1
ARRAY_OUTPUTSI := FALSE;
function block reuse in 1993. It is important to consider robustness of the
This is easier to transfers, no Steep Curve, no benefit from