Siemens Simatic S7 Series User manual

Siemens
Simatic S7
Manuals and Guides
Presented By: Siemens Supply
For Product Needs Please Visit:
http://www.siemenssupply.com/
OR email:
[e-mail]
OR call:
1-800-793-0630
Siemens S7 Manuals Siemens Supply www.siemenssupply.com

1
Table of Contents
Introduction ..............................................................................2
PLCs .........................................................................................4
Number Systems......................................................................8
Terminology ............................................................................ 12
Basic Requirements................................................................18
S7-200 Micro PLCs.................................................................20
Programming a PLC................................................................33
Discrete Inputs/Outputs .........................................................41
Analog Inputs and Outputs.....................................................48
Timers.....................................................................................51
Counters .................................................................................58
High-Speed Instructions .........................................................61
Specialized Expansion Modules .............................................65
Review Answers.....................................................................72
Final Exam .............................................................................. 74
www.siemenssupply.com

2
Introduction
Welcome to another course in the STEP series, Siemens
Technical Education Program, designed to prepare our
distributors to sell Siemens Industry, Inc. products more
effectively.This course covers Basics of PLCs and related
products.
Upon completion of Basics of PLCs you should be able to:
• Identify the major components of a PLC and describe
their functions
• Convert numbers from decimal to binary, BCD, and
hexadecimal
• Identify typical discrete and analog inputs and outputs
• Identify key differences of the various S7-200 models
• Identify the types of expansion modules available for
S7-200 PLCs
• Describe the types or programming available for S7-200
PLCs
• Describe the operation of commonly used program
functions such as timers and counters
• Identify the proper manual to refer to for programming or
installation of an S7-200 PLC
This knowledge will help you better understand customer
applications. In addition, you will be better able to describe
products to customers and determine important differences
between products.You should complete Basics of Electricity
before attempting Basics of PLCs. An understanding of many
of the concepts covered in Basics of Electricity is required for
this course.
After you have completed this course, if you wish to determine
how well you have retained the information covered, you can
complete a final exam online as described later in this course. If
you pass the exam, you will be given the opportunity to print a
certificate of completion.
www.siemenssupply.com

3
Siemens is a trademark of Siemens AG. Product names
mentioned may be trademarks or registered trademarks of their
respective companies. Specifications subject to change without
notice.
www.siemenssupply.com

4
PLCs
A programmable logic controller (PLC), also referred to as
a programmable controller, is the name given to a type of
computer commonly used in commercial and industrial control
applications. PLCs differ from office computers in the types of
tasks that they perform and the hardware and software they
require to perform these tasks. While the specific applications
vary widely, all PLCs monitor inputs and other variable values,
make decisions based on a stored program, and control
outputs to automate a process or machine.This course is
meant to supply you with basic information on the functions
and configurations of PLCs with emphasis on the S7-200 PLC
family.
SF/DIAG
Motor
Pump
Pushbutton
Sensor
Indicator Light
Basic PLC Operation The basic elements of a PLC include input modules or points,
a central processing unit (CPU), output modules or points,
and a programming device. The type of input modules or
points used by a PLC depends upon the types of input devices
used. Some input modules or points respond to digital inputs,
also called discrete inputs, which are either on or off. Other
modules or inputs respond to analog signals.These analog
signals represent machine or process conditions as a range of
voltage or current values. The primary function of a PLC’s input
circuitry is to convert the signals provided by these various
switches and sensors into logic signals that can be used by the
CPU.
www.siemenssupply.com

5
The CPU evaluates the status of inputs, outputs, and other
variables as it executes a stored program.The CPU then sends
signals to update the status of outputs.
Output modules convert control signals from the CPU into
digital or analog values that can be used to control various
output devices.
The programming device is used to enter or change the PLC’s
program or to monitor or change stored values. Once entered,
the program and associated variables are stored in the CPU.
In addition to these basic elements, a PLC system may also
incorporate an operator interface device to simplify monitoring
of the machine or process.
Programming
Device
Operator
Interface
Central Processing Unit
(CPU)
Input
Module
Output
Module
In the simple example shown below, pushbuttons (sensors)
connected to PLC inputs are used to start and stop a motor
connected to a PLC output through a motor starter (actuator).
No programming device or operator interface are shown in this
simple example.
Motor Starter
Start
Pushbutton
Stop
Pushbutton
Inputs
Output
PLC
Motor
SF/DIAG
www.siemenssupply.com

6
Hard-Wired Control Prior to PLCs, many control tasks were performed by
contactors, control relays, and other electromechanical devices.
This is often referred to as hard-wired control. Circuit
diagrams had to be designed, electrical components specified
and installed, and wiring lists created. Electricians would then
wire the components necessary to perform a specific task. If
an error was made, the wires had to be reconnected correctly.
A change in function or system expansion required extensive
component changes and rewiring.
OL
M
CR
CR
L1
T1
T2
T3
L2
L3
OL
OL
OL
M
M
CR
M
Motor
Start
Stop
460 VAC
24 VAC
1
2
Advantages of PLCs PLCs not only are capable of performing the same tasks as
hard-wired control, but are also capable of many more complex
applications. In addition, the PLC program and electronic
communication lines replace much of the interconnecting wires
required by hard-wired control. Therefore, hard-wiring, though
still required to connect field devices, is less intensive.This also
makes correcting errors and modifying the application easier.
Some of the additional advantages of PLCs are as follows:
• Smaller physical size than hard-wire solutions.
• Easier and faster to make changes.
• PLCs have integrated diagnostics and override functions.
• Diagnostics are centrally available.
• Applications can be immediately documented.
• Applications can be duplicated faster and less expensively.
Siemens Modular PLCs Siemens SIMATIC PLCs are the foundation upon which our
Totally Integrated Automation (TIA) concept is based.
Because the needs of end users and machine builders vary
widely, SIMATIC PLCs are available as conventional modular
controllers, embedded automation products, or as PC-based
controllers.
www.siemenssupply.com

7
Modular SIMATIC controllers are optimized for control tasks
and can be adapted to meet application requirements using
plug-in modules for input/output (I/O), special functions, and
communications. Examples of products in this category include:
LOGO!, S7-200, and S7-1200 micro automation products,
S7-300 and S7-400 modular system PLCs, C7 combination
controller and panel, and ET 200 distributed I/O system with
local intelligence.
SIMATIC S7-400 SIMATIC S7-300
SIMATIC S7-200 LOGO!
SF/DIAG
SIMATIC
S7-1200
SIMATIC S7-1200
Other SIMATIC Controllers SIMATIC embedded automation products are available in
a microbox, panel PC, or multi-functional PC-based system.
All products utilize rugged, fan-free, diskless hardware
platforms with an operating system optimized for each
platform. Examples of products in this category include:
Microbox 420-RTX, Microbox 420-T, Panel PC 477-HMI/RTX, and
WinAC MP.
SIMATIC PC-based controllers are available as software that
can run on standard PC systems or in a plug-in card (slot PLC)
for increased reliability.This category includes WinAC software
and WinAC slot PLC.
SIMATIC Software SIMATIC software is the universal configuring and
programming environment for SIMATIC controllers, human
machine interface systems, and process control systems.
SIMATIC software with STEP 7 and numerous engineering
tools supports all phases of product deployment, from
hardware configuration of the system and parameterization
of modules to service of the installed system. A variety
of programming options are available.This includes basic
programming languages (Instruction List, Ladder Diagram,
and Function Block Diagram), high-level languages (Structured
Text and Sequential Function Chart), and engineering tools
(S7 Structured Control Language, S7-Graph, S7-PLCSIM, S7-
HiGraph, and Continuous Function Chart).
www.siemenssupply.com

8
Number Systems
Because a PLC is a computer, it stores information in the form
of on or off conditions (1 or 0), referred to as bits. Sometimes
bits are used individually and sometimes they are used
to represent numerical values. Understanding how these
bits can be used to represent numerical values requires an
understanding of the binary number system.
Decimal System In order to understand the binary number system, it is
first useful to recall some of the basics of the decimal
number system. All number systems have the same three
characteristics: digits, base, weight. For example, the decimal
system has the following characteristics:
Ten digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
Base 10
Weights Powers of base 10 (1, 10, 100, 1000, ...)
Binary System The binary system has the following characteristics:
Two digits: 0, 1
Base 2
Weights Powers of base 2 (1, 2, 4, 8, 16, ...)
The binary system has a base of 2 and uses only two
characters, 1 and 0. Each bit is associated with a power of 2
based on its position in the number. The further to the left,
the higher the power of 2.The number in the far left-hand
column is referred to as the most significant bit or MSB and
the number in the far right-hand column is referred to as the
least significant bit or LSB. A 1 is placed in a position if that
power of 2 is used in the number. Otherwise, a 0 is placed in a
position.
128 64 32 16 8 4 2 1
0 0 0 1 1 0 0 0
Most Significant Bit (MSB) Least Significant Bit (LSB)
2726252423222120
00011000 in binary = 24 in Decimal
www.siemenssupply.com

9
The process of converting a binary number to an equal decimal
value is as simple as adding the equivalent decimal value
for each position in the binary number where a 1 is shown.
Positions with a 0 do not add to the number value.
128 64 32 16 8 4 2 1
0 0 11 0 0
2726252423222120
1 0
Decimal Value = 32 + 8 + 1 = 41
Bits, Bytes, and Words Each position in a binary number is called a bit. The number
of bits used to represent numbers varies with the device.
However, instructions and data are usually grouped in bytes and
eight bits make up one byte.Two bytes, or 16 bits, make up one
word.
Word
Byte
Bit
Logic 0, Logic 1 While PLCs are capable of sensing and generating analog
values, programmable controllers internally use signals that are
on or off. These on and off conditions correspond to the binary
values 1 and 0. For example, a binary 0, also called logic 0, can
be used to indicate that a switch is off, and a binary 1 (logic 1)
can be used to indicate that a switch is on.
PLC
Input 1
24 VDC
Off
Logic 0
On
Logic 1 PLC
Input 1
24 VDC
www.siemenssupply.com

10
BCD While it is necessary for PLCs to use binary values, humans
often need to see values represented in decimal. As a result,
some input and output devices provide a decimal display where
each decimal digit corresponds to four PLC binary inputs or
outputs.The most common system used by input and output
devices of this type is referred to as binary-coded decimal
(BCD).
One example of a BCD device is a type of four-digit
thumbwheel switch. Each thumbwheel digit controls four
PLC inputs.This means that for a four-digit thumbwheel, 16
inputs are required. Because each thumbwheel digit only
needs to represent decimal values from 0 through 9, only ten
corresponding binary values are required for each digit.
0205
0000 0010 0000 0101
Decimal
0 0 0 0 0
1 0 0 0 1
2 0 0 1 0
3 0 0 1 1
4 0 1 0 0
5 0 1 0 1
6 0 1 1 0
7 0 1 1 1
8 1 0 0 0
9 1 0 0 1
BCD
Hexadecimal Hexadecimal is another system used in PLCs. The ten digits
of the decimal system are used for the first ten characters of
the hexadecimal system.The first six letters of the alphabet are
used for the remaining six characters.
The hexadecimal system is used in PLCs because it allows the
status of a large number of binary bits to be represented in a
small space such as on a computer screen or programming
device display. Each hexadecimal character represents the exact
status of four binary bits.
Hexadecimal Number System
16 digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
Base 16
Weights Powers of base 16 (1, 16, 256, 4096, ...)
Hexadecimal
0 0 0 0 0
1 0 0 0 1
2 0 0 1 0
3 0 0 1 1
4 0 1 0 0
5 0 1 0 1
6 0 1 1 0
7 0 1 1 1
8 1 0 0 0
9 1 0 0 1
A 1 0 1 0
B 1 0 1 1
C 1 1 0 0
D 1 1 0 1
E 1 1 1 0
F 1 1 1 1
Binary
Hexadecimal Example
Binary Equivalent 0011101000101111
F
3
A
2
www.siemenssupply.com

11
Review 1
1. Identify each of the following blocks in a basic PLC
system:
d. _______ e. _______
b. ______________
a. ______ c. ______
2. The base of the binary number system is ___ .
3. The base of the hexadecimal number system is ___.
4. Convert the decimal number 10 to each of the following
number types:
Binary ____________
BCD ____________
Hexadecimal ____________
www.siemenssupply.com

12
Terminology
Developing an understanding of PLCs requires learning
some basic terminology. This section provides an overview of
commonly used PLC terms, beginning with the terms sensor
and actuator.
Sensors Sensors are devices that convert a physical condition into an
electrical signal for use by a controller, such as a PLC. Sensors
are connected to the input of a PLC. A pushbutton is one
example of a sensor that is often connected to a PLC input. An
electrical signal indicating the condition (open or closed) of the
pushbutton contacts is sent from the pushbutton to the PLC.
Actuators Actuators are devices that convert an electrical signal from a
controller, such as a PLC, into a physical condition. Actuators are
connected to the PLC output. A motor starter is one example of
an actuator that is often connected to a PLC output. Depending
on the status of the PLC output, the motor starter either
provides power to the motor or prevents power from flowing to
the motor.
Motor
Sensor Actuator
Central
Processing
Unit
(CPU)
Input
Point
Output
Point
PLC
Motor
Starter
Pushbutton
Discrete Input Discrete Output
Discrete Inputs and Outputs Discrete inputs and outputs, also referred to as digital
inputs and outputs, are either on or off. Pushbuttons, toggle
switches, limit switches, proximity switches, and relay contacts
are examples of devices often connected to PLC discrete
inputs. Solenoids, relay and contactor coils, and indicator lamps
are examples of devices often connected to PLC discrete
outputs.
In the on condition, a discrete input or output is represented
internal to the PLC as a logic 1. In the off condition, a discrete
input or output is represented as a logic 0.
www.siemenssupply.com

13
Analog Inputs and Outputs Analog inputs and outputs are continuous, variable signals.
Typical analog signals vary from 0 to 20 milliamps, 4 to
20 milliamps, or 0 to 10 volts.
In the following example, a level transmitter monitors the level
of liquid in a storage tank and sends an analog signal to a PLC
input. An analog output from the PLC sends an analog signal to
a panel meter calibrated to show the level of liquid in the tank.
Two other analog outputs, not shown here, are connected to
current-to-pneumatic transducers that control air-operated flow-
control valves.This allows the PLC to automatically control the
flow of liquid into and out of the storage tank.
Central
Processing
Unit
(CPU)
Analog
Input
Analog
Output
PLC
0
0.2
0.4
0.6
0.8
1.0
Level
Transmitter
Storage
Tank
Panel
Meter
CPU The central processor unit (CPU) is a microprocessor system
that contains the system memory and is the PLC’s decision-
making unit.The CPU monitors inputs, outputs, and other
variables and makes decisions based on instructions held in its
program memory.
SF/DIAG
I0.0 I0.1 Q0.0
Q0.1
I0.4
I0.5
www.siemenssupply.com

14
Ladder Logic Programming A program consists of instructions that accomplish specific
tasks.The degree of complexity of a PLC program depends
upon the complexity of the application, the number and type of
input and output devices, and the types of instructions used.
Ladder logic (LAD) is one programming language used with
PLCs. Ladder logic incorporates programming functions that are
graphically displayed to resemble symbols used in hard-wired
control diagrams.
The left vertical line of a ladder logic diagram represents the
power or energized conductor.The output coil instruction
represents the neutral or return path of the circuit.The right
vertical line, which represents the return path on a hard-wired
control line diagram, is omitted. Ladder logic diagrams are read
from left-to-right and top-to-bottom. Rungs are sometimes
referred to as networks. A network may have several control
elements, but only one output coil.
Power Conductor
Network 1
Network 2
I0.0 I0.1 Q0.0
Output Coil Instruction
Normally Open Contact Instructions
I0.4
I0.5
Q0.0
Statement List and While ladder logic programs are still common, there are many
Function Block Diagrams other ways to program PLCs. Two other common examples are
statement list and function block diagrams.
Statement list (STL) instructions include an operation and an
operand.The operation to be performed is shown on the left.
The operand, the item to be operated on, is shown on the right.
Function block diagrams (FBD) include rectangular functions
with inputs shown on the left side of the rectangle and outputs
shown on the right side.
www.siemenssupply.com

15
In the following example, the program segments perform the
same function.
Network 1
Network 2
I0.0 I0.1 Q0.0
I0.4
I0.5
Q0.0
Network 1
LD
A
=
I0.0
I0.1
Q0.0
LD
O
=
I0.4
I0.5
Q0.1
Network 2
AND
I0.0
I0.1 Q0.0
OR Q0.1
I0.4
I0.5
Network 1
Network 2
Statement List (STL) Function Block Diagram (FBD) Ladder Logic (LAD)
In addition to LAD, STL, and FBD, multiple other types of
programming languages are used for PLCs. Each type of
programming has its advantages and disadvantages. Factors
such as application complexity, types of programming available
for a specific PLC model, and user standards and preferences
determine which type of programming is used for an
application.
PLC Scan The PLC program is executed as part of a repetitive process
referred to as a scan. A PLC scan starts with the CPU
reading the status of inputs. Next, the application program is
executed.Then, the CPU performs internal diagnostics and
communication tasks. Finally, the CPU updates the status of
outputs.This process repeats as long as the CPU in the run
mode.The time required to complete a scan depends on the
size of the program, the number of I/Os, and the amount of
communication required.
PLC Scan
R
e
a
d
I
n
p
u
t
s
E
x
e
c
u
t
e
P
r
o
g
r
a
m
D
i
a
g
n
o
s
t
i
c
s
&
C
o
m
m
u
n
i
c
a
t
i
o
n
U
p
d
a
t
e
O
u
t
p
u
t
s
www.siemenssupply.com

16
MemoryTypes and Size Kilo, abbreviated k, normally refers to 1000 units. When talking
about computer or PLC memory, however, 1k means 1024. This
is because of the binary number system (210=1024). 1k can refer
to 1024 bits, bytes, or words, depending the context.
Random Access Memory (RAM) is memory that allows data
to written to and read from any address (location). RAM is used
as a temporary storage area. RAM is volatile, meaning that
the data stored in RAM will be lost if power is lost. A battery
backup is required to avoid losing data in the event of a power
loss.
Read Only Memory (ROM) is a type of memory used were
it is necessary to protect data or programs from accidental
erasure.The original data stored in ROM can be read, but
not changed. In addition, ROM memory is nonvolatile.This
means that information will not be lost as the result of a loss of
electrical power. ROM is normally used to store the programs
that define the capabilities of the PLC.
Erasable Programmable Read Only Memory (EPROM)
provides a level of security against unauthorized or unwanted
changes in a program. EPROMs are designed so that data
stored in them can be read, but not easily altered. Changing
EPROM data requires a special effort. UVEPROMs (ultraviolet
erasable programmable read only memory) can only be erased
with an ultraviolet light. EEPROM (electronically erasable
programmable read only memory), can only be erased
electronically.
Software, Hardware, and Software is the name given to computer instructions,
Firmware regardless of the programming language. Essentially, software
includes the instructions or programs that direct hardware.
Hardware is the name given to all the physical components
of a system.The PLC, the programming device, and the
connecting cable are examples of hardware.
Firmware is user or application specific software burned into
EPROM and delivered as part of the hardware. Firmware gives
the PLC its basic functionality.
www.siemenssupply.com

17
Putting it Together The user memory of a PLC, such as the S7-200 PLC shown in
the following illustration, includes space for the user program as
well as addressable memory locations for storage of data. The
amount of program and data space available depends on the
CPU model.
User program space stores instructions that are executed
repetitively as part of the PLC scan. The user program is
developed using a programming device, such as a personal
computer (PC) with programming software, then loaded into the
user program memory of the PLC.
A variety of addressable memory locations are used for storage
of data that is available to the user program. Among other
things, this includes memory locations for variable data, discrete
inputs and outputs, analog inputs and outputs, timers, counters,
high-speed counters, etc.
I0.0 I0.1 Q0.0
Q0.1
I0.4
I0.5
www.siemenssupply.com

18
Basic Requirements
Throughout this course we will be using the S7-200 PLC for
specific examples of PLC concepts.The S7-200 PLC is used
for this purpose because of its ease of use and wide-spread
application.
The items shown in the following illustration are needed to
create or change an S7-200 PLC program.The program is
created using STEP 7-Micro/WIN programming software,
which runs on a Windows-based personal computer (Win2000,
Windows XP, and higher operating system).
A special cable is needed when a personal computer is used as
a programming device.Two versions of this cable are available.
One version, called an RS-232/PPI Multi-Master Cable,
connects a personal computer’s RS-232 interface to the PLC’s
RS-485 connector. The other version, called a USB/PPI Multi-
Master Cable, connects a personal computer’s USB interface
to the PLC’s RS-485 connector.
SF/DIAG
Software
STEP 7 - Micro/WIN
Programming Device
Programming Device Cable
S7-200 PLC
www.siemenssupply.com

19
Review 2
1. Pushbuttons, limit switches, and relay contacts are
examples of devices that may be connected to PLC
____________ inputs.
2. Solenoids, relay and contactor coils, and indicator lamps
are examples devices that may be connected to PLC
___________ outputs.
3. The _____ contains the system memory and makes
decisions based on instructions stored in program
memory.
4. ______ _____ is a PLC programming language that
incorporates programming functions that are graphically
displayed to resemble symbols used in hard-wired
control diagrams.
5. _________ ____ and ________ _____ ________ are also
common examples of ways to program a PLC.
6. A PLC program is executed as part of a repetitive
process referred to as a ____.
7. When talking about computer or PLC memory, 1k refers
to ______ bits, bytes, or words.
8. Software that is burned into EPROM is called
____________.
9. An RS-232/PPI Multi-Master cable or a USB/PPI-Multi-
Master cable may be used to connect a personal
computer to an S7-200 PLC’s __________ connector.
www.siemenssupply.com