Input and Output Addressing in Siemens PLC - Tia Portal Tutorial

Summary

Today's lecture covers input/output and memory addressing in Siemens PLCs. It explains the basics of digital and analog I/O, memory storage units like bits, bytes, words, and double words, and data types including Boolean, string, integer, and float. The lecture distinguishes between digital (Boolean) and analog (integer/float) signal addressing. It also details how PLCs convert sensor signals into machine-readable data, using signed and unsigned integers. The addressing format for digital and analog I/O in PLCs is discussed, highlighting identifiers like 'I' for inputs, 'Q' for outputs, and 'W' for analog word addressing.

Takeaways

• 💡 Digital inputs and outputs are categorized as digital signals, while analog inputs and outputs correspond to analog signals.
• 📊 Data in Siemens PLC is stored in bits (zeros and ones), and various units such as byte (8 bits), word (16 bits), and double word (32 bits) are used for memory addressing.
• 🔢 There are four main data types in PLC programming: boolean (0 or 1), string (characters), integer (both positive and negative values), and float (decimal values).
• 📉 Boolean data types are used for digital signals, while integer and float data types are used for analog signals.
• 🎛️ Addressing is divided into two categories: I/O addressing for input/output terminals and memory addressing for internal memory of the PLC.
• ⚙️ Unsigned integers only store positive values, while signed integers include both positive and negative values, determined by the presence of a sign before the value.
• 🧮 The number of possible states using bits is calculated as 2^n, where n is the number of bits. For example, 2 bits give 4 states, 8 bits give 256 states.
• 🔢 In Siemens PLCs, I/O addressing for inputs uses the 'I' identifier, and output addressing uses the 'Q' identifier.
• 🧾 Analog inputs and outputs use word addressing, which consists of 16 bits to handle the data (e.g., IW for input word, QW for output word).
• 🔄 Digital inputs and outputs increment the address after 8 bits (from 0 to 7), while analog addresses update in steps of 2 (IW 128, IW 130).

Q & A

What are the two main categories of inputs and outputs in Siemens PLCs?

The two main categories of inputs and outputs in Siemens PLCs are digital inputs/outputs and analog inputs/outputs.

What is a bit, and how does it relate to a byte and a word?

A bit is the smallest unit of data and represents either 0 or 1. A byte is a combination of 8 bits, and a word is a combination of 2 bytes or 16 bits.

What are the four main data types used in PLC programming?

The four main data types used in PLC programming are boolean, string, integer, and float. Boolean represents digital signals (0 or 1), strings represent characters, integers represent whole numbers, and floats represent decimal values.

What is the difference between signed and unsigned integers?

Unsigned integers only represent non-negative values (0 and above), while signed integers can represent both positive and negative values by including a sign before the value.

How many states can be represented using 2 bits?

Using 2 bits, 4 states can be represented, which are 00, 01, 10, and 11.

What is the range of values that can be represented using 8 bits for signed and unsigned integers?

For unsigned integers, 8 bits can represent values from 0 to 255. For signed integers, the range is from -128 to +127.

What is the function of IO addressing in a PLC?

IO addressing in a PLC is used to address the input and output terminals, allowing the PLC to manage the signals from and to sensors and actuators.

What do the identifiers 'I' and 'Q' represent in Siemens PLC addressing?

'I' represents input addressing, while 'Q' represents output addressing in Siemens PLCs.

What does 'W' represent in Siemens PLC addressing for analog signals?

'W' represents word addressing, which is used for analog inputs and outputs in Siemens PLCs, where data is usually represented in 16 bits.

How does the PLC convert analog signals such as current or voltage into data that the processor can understand?

The PLC converts analog signals like 4-20mA or 0-10V into digital data by converting the signals into binary form, which the processor can then interpret as integer or float values.

Outlines

00:00

🔌 Introduction to Input, Output, and Memory Addressing in Siemens PLC

This paragraph introduces the basic concepts of input, output, and memory addressing in Siemens PLC. It explains the two primary types of input and output (digital and analog) and provides an overview of how data, such as bits, bytes, words, and double words, is stored in memory. The explanation continues by breaking down data types used in PLC programming: Boolean (for digital signals), String (for characters), Integer (for a wide range of values), and Float (for decimal values). It also highlights the difference between addressing for digital and analog signals.

05:00

⚙️ IO and Memory Addressing in Siemens PLCs

This section further delves into the two types of addressing: I/O addressing (for input and output terminals) and memory addressing (for internal bits stored in the PLC's memory). It explains that processors in PLCs can only interpret machine language and describes how incoming signals from sensors, typically in the form of current or voltage, are converted into data that the processor can understand. It also introduces signed and unsigned integers, explaining the distinction between them and illustrating how integer values are represented in both forms.

10:00

🔢 Representation of Data Using Bits

This paragraph explains how data is represented using bits. Starting with two bits, it shows how different states (e.g., 00, 01, 10, 11) map to values for unsigned integers. It extends this logic to 8 bits, explaining how unsigned and signed integers are represented across a range of values. For example, 8-bit unsigned integers can represent values from 0 to 255, while signed integers are divided into negative and positive halves, spanning from -128 to 127. The concept is expanded to 16-bit and 32-bit representations, which significantly increase the number of possible values.

🔌 Digital Inputs, Outputs, and Addressing in Siemens PLCs

This section introduces the addressing format used for digital inputs and outputs in Siemens PLCs. For digital inputs, addresses follow the format 'I' (input) followed by byte and bit numbers (e.g., I0.0 to I0.7). The concept of byte updates after 8 bits are processed is also explained. Similarly, output addressing uses 'Q' (for output), such as Q0.0 to Q0.7. This part emphasizes how addressing updates occur and the role of identifiers (I for input, Q for output) in distinguishing between input and output terminals.

📊 Analog Inputs, Outputs, and Word Addressing

This paragraph focuses on addressing for analog inputs and outputs in Siemens PLCs. Analog signals, often coming in the form of current or voltage (e.g., 4–20 mA), are represented using word addressing due to their larger data size. Input addresses for analog signals are formatted as 'IW' (e.g., IW128 for input words), while outputs use 'QW' (e.g., QW144 for output words). The paragraph also mentions the specific structure of these addresses and hints at why certain addresses (like 128 and 130) are used for analog signals.

Keywords

💡Input/Output

Input/Output (I/O) refers to the communication channels between a system and the external devices or interfaces. In the context of the video, I/O is crucial for Siemens PLCs (Programmable Logic Controllers) to interact with sensors and actuators. The script mentions digital inputs and outputs, which are binary signals that can be either on or off, and analog inputs and outputs, which can have a range of values. For instance, digital inputs might be connected to switches or buttons, while analog inputs could be connected to temperature sensors.

💡Memory Addressing

Memory Addressing pertains to how data is stored and accessed within a system's memory. In the video, memory addressing is essential for PLC programming as it allows the processor to interact with data stored in memory. The script explains that there are two types of addressing: I/O addressing, which refers to the physical input and output terminals, and memory addressing, which is the internal addressing within the PLC's memory.

💡Bits and Bytes

Bits and Bytes are fundamental units of data storage. A bit is the smallest unit of data, representing a 0 or 1, while a byte consists of 8 bits. The video script uses these terms to explain how data is represented in the PLC's memory. For example, the script mentions that a byte is a combination of 8 bits, which is a basic unit for data storage and manipulation in PLCs.

💡Boolean

Boolean is a data type that represents one of two values: true or false, which are equivalent to 1 or 0 in digital systems. In the video, Boolean is used to describe digital signals, such as the state of a switch, which can be either on (true) or off (false). The script emphasizes that Boolean values are crucial for handling digital inputs and outputs in PLC programming.

💡Integer

Integer is a data type representing whole numbers, both positive and negative. In the context of the video, integers are used to represent analog signals, such as sensor readings that can be converted into integer values. The script explains that integers can be signed (with a positive or negative sign) or unsigned (always positive), and this distinction is important for PLC programming as it affects how data is stored and manipulated.

💡Float

Float is a data type that represents real numbers, including fractions, in decimal form. The video script mentions that floats are used for analog signals, which can have a continuous range of values. For example, a temperature sensor might output a float value representing the current temperature as a decimal number.

💡Data Conversion

Data Conversion is the process of transforming data from one format to another. The script discusses how analog signals, such as 4-20 mA or 0-10V, are converted into digital values that the PLC's processor can understand. This conversion is a critical step in PLC programming as it allows the processor to handle and process analog data.

💡Digital Input/Output

Digital Input/Output refers to the binary signals that are either on or off. In the video, digital inputs are connected to addresses like I0.0, I0.1, etc., and digital outputs are addressed as Q0.0, Q0.1, etc. These are used for simple on/off control in automation systems, such as turning a light on or off.

💡Analog Input/Output

Analog Input/Output handles signals that can vary over a continuous range of values. In the script, analog inputs are addressed starting from IW128, and analog outputs from QW144. These are used for more complex control tasks that require a range of values, such as controlling the speed of a motor or adjusting the temperature in a heating system.

💡Identifiers

Identifiers are used to label and distinguish different elements in a program or system. In the video, 'I' and 'Q' are identifiers used to distinguish between input and output terminals in PLC addressing. The script explains that 'I' is used for inputs and 'Q' for outputs, helping to organize and manage the connections in a PLC system.

💡Machine Language

Machine Language is the low-level language understood by a computer's hardware. The video script mentions that a processor understands machine language, and the data from sensors, such as current or voltage signals, must be converted into a form that the processor can understand. This conversion is a fundamental aspect of PLC programming, allowing the processor to interpret and act on input signals.

Highlights

Introduction to input, output, and memory addressing in Siemens PLCs.

Types of input and output: Digital (digital input, digital output) and Analog (analog input, analog output).

Basic data storage in PLCs: bits, bytes (8 bits), words (16 bits), and double words (32 bits).

Four essential data types: Boolean (0 or 1), String (characters), Integer (range from negative to positive infinity), and Float (decimal values).

Boolean data type is used for digital signals, while Integer and Float are used for analog signals.

PLCs use I/O addressing for input/output terminals and memory addressing for internal bits.

Unsigned integers include only positive values, while signed integers include both positive and negative values.

Using two bits, we can represent four states in unsigned integers: 00, 01, 10, and 11.

With 8 bits, unsigned integers can range from 0 to 255, while signed integers range from -128 to 127.

Explanation of 16-bit unsigned integers (range from 0 to 65535) and signed integers (range from -32768 to 32767).

32-bit signed integers range from -2147483648 to [phone].

Digital inputs and outputs have specific I/O addressing formats (e.g., i0.0, q0.0 for Siemens PLCs).

Analog input and output use word addressing (e.g., iw128, qw144 for Siemens PLCs).

Identifiers such as 'i' for input, 'q' for output, and 'w' for word are used to distinguish between analog and digital signals.

Addressing in Siemens PLCs is carried forward after completing eight bits (byte completion updates the next address).

Transcripts

[Music]

[Music]

hello everyone so in today's lecture we

are going to discuss about input output

and memory addressing in siemens plc

okay so basically input types and output

types basically can be divided into two

categories so basically digital input

and digital outputs similarly in case of

analog there will be analog input and

analog outputs right so

now before moving further we should know

these are some of the basic

terminologies about how the data is

stored inside the memory okay bits are

what zeros and ones similarly if you

talk about byte so byte is basically

combination of 8 bits similarly if you

talk about the word the word is

basically combination of 2 bytes or 16

bits

similarly if you talk about double word

double word will be the combination of

two words or four bytes or 32 bits right

data types can be categorized into four

types okay so basically boolean means

what boolean is basically zero or one

state okay so used for digital signals

similarly if you talk about string

strings are basically characters

integer means what basically a value

existing from minus infinite to plus

infinite it can be any of the value

between these okay so similarly if you

talk about float so float is basically a

data type which contains the value which

are in decimal okay so

these are basically the four types of

data types which will be very important

in case of our plc programming okay

now important point here to notice the

integer and float addressings are for

analog signals okay so boolean is

basically for

uh digital signals okay and

integer and float addressings are for

analog okay

so addressing can be divided into two

categories okay so first one is io

addressing and second one is memory

addressing

in case of io addressing this is the

addressing of the input terminals and

the output terminals of the plc

okay similarly memory addressing it is

inside the memory of the plc okay so

addressing can be divided into two

categories first one is io addressing

and second one is memory addressing in

case of io addressing basically this is

the addressing of the

input and output terminals of the plc

and similarly if you talk about the

memory addressing it is basically the

addressing of input bits or we can say

the internal bits of the plc's memory

okay now

we should note that a processor can

always understand machine language okay

so the data which is coming in the form

of

integer values from the sensors that

will be in the form of a current or

voltage that is from 4 to 20 milliampere

or 0 to 10 volt signal then this signal

will be converted into uh such a form

that it can be understandable or we can

say the processor can understand that

data so

how this data is converted to

bits that is the that is what we are

going to see here so first of all we

should know that the integers can be

categorized into two forms that is

signed and unsigned integers right so if

you talk about

unsigned integers the values which don't

have any sign

all those values are called as unsigned

integers right so here

all the values from 0 or above 0 all

these are called positive values so all

this will be defined under unsigned

integers right so if you are having only

positive values uh then

we can write it without any sign also

for example if you are writing 4 so the

4 value is not having any sign so by

default it will be positive only ok

similarly if you talk about signed

integers in case of signed integers

there will be

sign present before the value okay so

here if you observe

minus 2 plus 1 okay so minus 2 is also a

value which is having negative sign

similarly plus 1 is having positive sign

so basically it is a signed integer okay

so any value suppose plus 4 that is

having a sign that means it is a signed

integer okay or understood what is the

difference between signed and unsigned

integers right now we'll be seeing how

this bit data is converted into integer

form okay if you take two bits right

suppose we are having two bits so how

many states are possible basically 2 to

the power 2 is how much 4 so 4 states

are possible using 2 bits right so 0 0 0

1 1 0 1 1 okay so

basically we can have four states with

it okay so

uh zero zero means what zero value

similarly if you talk about zero one

that is one similarly if you talk about

one zero that will be

two and similarly if you talk about 1 1

that will be 3 this is how we can write

in case of unsigned integers from 0 to 3

right similarly in case of signed

integers will be having it from minus 2

to plus 1 okay

now

similarly if you take 8 bits okay how

many values can be represented using 8

bits so 2 to the power 8 is 2 to 256

right so in case of unsigned integers if

you talk about unsigned integers means

what here all the positive values

including 0 will be there so we can go

from 0 to 255 why because

256

total 256 values can be represented so 0

is all always considered in case of

positive so

if 0 is the one value then remaining

there are 255 more values which can be

represented using unsigned integer

using 8 bits right similarly if you talk

about signed integers so half of it will

be divided here if you observe

if you talk about 256 so if you divide

it by 2 then

we will be getting 128 okay so

in case of if you talk about signed

integers from minus 128 to 0 that means

how many values 128 values for negative

and from 0 to 127 that is 0 is also

included in it that means we are having

again positive 128 values and negative

128 values that means total we are

having 256 values so in case of signed

values we can say from minus 128 to plus

127 okay now if we talk about 16 bits so

2 to the power 16 is 65536

so again in case of unsigned integers

from zero

from zero to six five five three five

and in case of signed integers it will

be divided into half okay

in two halves means what minus three two

seven six eight two plus three two seven

six seven zero is also included in

positive that is why it is three two

seven six seven similarly in case of

thirty two bits okay thirty two bits

mean means what we are having one word

that is 2 to the power 32 is

4 2 9 4 9 6 7 2 9 6 okay so again we'll

be having 0 to 4 2 9 4 9 6 7 2 9 5 okay

similarly if you talk about signed

integers so again it will be divided

into half minus two one four seven four

eight three six four eight two plus two

one four seven four eight three six four

seven okay now if you talk about the i o

addressing okay now

in case of plcs okay so we'll be having

digital inputs digital outputs analog

input and analog output so in case of

plc's we will be having terminals okay

so there will be connecting our wires or

the signals coming from the pl uh

sensors right so in case of digital

inputs so digital inputs will be

connected to the following addresses

right so

the addresses are like this i zero dot

zero okay i zero dot one i zero dot two

i zero dot three in this way we are

moving okay so here if you observe these

are basically zero one 2 3

4 5 6 7 so this is what these are the

input bits okay so these are what input

bits similarly if you observe

this value is 0 that means these are

word bytes okay so basically it is zero

byte which is having eight bits okay so

zero to seven there are total eight bits

and this is what byte okay so it will be

updated when

these total 1 byte is completed so 0 to

7 there are total 8 bits so it is

completed now so it will be updated now

see if you observe here there is one

okay so

after completing that

one or we can say now the value has

updated to one here okay now

again it will complete the same and

again then after 0 to 7 it will again

update itself to 2 in this way the

addressing will be carry forwarded okay

now similarly if it

here one more important thing is i so i

is basically the identifier okay so

identifier is basically used to identify

whether it is input or output now in

case of

siemens plcs the output addressing is in

the form of q0 dot zero see here if you

observe this is one of the output bits

okay so output is not represented by o

okay so output is not represented by o

here we will be using the addressing in

the form of q zero dot zero q

zero dot one q 0.2 in this way okay so

again if you observe from 0 to 7 it will

complete the total 8 bits and then only

it will update itself okay so here the

byte will be updated after completing

eight bits okay so in this way we are

using the output addressing format okay

similarly if you talk about analog

inputs

so analog are basically the values so

obviously it will be in the form of word

okay so basically

in

previous

slide we have seen that if the analog

inputs are present so what will be using

word okay so word is basically what 16

bits to represent any values so the data

will be coming in the form of 4 to 20

milliampere so it has to be converted in

some other form

that is

binary language form that is why we need

to use this kind of addressing okay here

if you observe this is what iw 128 that

is what word addressing okay so i w is

basically i is representing what analog

input okay here in case of

a i it is representing analog input and

similarly if you talk about analog

output this is like this qw 144 qw

okay so here one

uh you might have observed why

after 128 130 is given so uh we'll be

discussing it in uh the upcoming slides

right why it is so okay now so digital

inputs will be uh i zero dot zero i zero

dot to i zero dot seven similarly after

that uh

i one dot zero i one dot one and it will

go up to i 1.7 and again then it will be

updating itself so it will be i

2 dot

1 i 2 dot 2 in this way okay similarly

if you talk about digital outputs so the

addressing will be q 0 dot 0 give zero

dot

one q zero dot two in this way and

uh similarly analog inputs will be i w

zero i w two

okay and analog outputs will be q's w

zero q w two in this way will be having

okay so i and q are also called as

identifiers to represent the address if

it is input or output okay so uh

to identify whether it is an input or

output terminal here what will be using

i and q okay and similarly w represents

the word addressing for analog inputs or

output so whether you want to

if you want to identify whether it is

analog input or digital input we can

identify it using

if we find w here okay so w means what

for analog that is representing the

world okay

[Music]

you