Siemens SIMATIC S7-200 User manual

Preface
Quick review 1
Latching 2
Pulse Operated Switch 3
Off Delay Timer 4
Sequencer 5
Learning More 6
Appendix A A
SIMATIC S7-200
S7-200
Getting Started - Advanced
Training Documents
09/2007
A5E01469795B

Safety Guidelines
This manual contains notices you have to observe in order to ensure your personal safety, as well as to prevent
damage to property. The notices referring to your personal safety are highlighted in the manual by a safety alert
symbol, notices referring only to property damage have no safety alert symbol. These notices shown below are
graded according to the degree of danger.
DANGER
indicates that death or severe personal injury will result if proper precautions are not taken.
WARNING
indicates that death or severe personal injury may result if proper precautions are not taken.
CAUTION
with a safety alert symbol, indicates that minor personal injury can result if proper precautions are not taken.
CAUTION
without a safety alert symbol, indicates that property damage can result if proper precautions are not taken.
NOTICE
indicates that an unintended result or situation can occur if the corresponding information is not taken into
account.
If more than one degree of danger is present, the warning notice representing the highest degree of danger will
be used. A notice warning of injury to persons with a safety alert symbol may also include a warning relating to
property damage.
Qualified Personnel
The device/system may only be set up and used in conjunction with this documentation. Commissioning and
operation of a device/system may only be performed by qualified personnel. Within the context of the safety notes
in this documentation qualified persons are defined as persons who are authorized to commission, ground and
label devices, systems and circuits in accordance with established safety practices and standards.
Prescribed Usage
Note the following:
WARNING
This device may only be used for the applications described in the catalog or the technical description and only
in connection with devices or components from other manufacturers which have been approved or
recommended by Siemens. Correct, reliable operation of the product requires proper transport, storage,
positioning and assembly as well as careful operation and maintenance.
Trademarks
All names identified by ® are registered trademarks of the Siemens AG. The remaining trademarks in this
publication may be trademarks whose use by third parties for their own purposes could violate the rights of the
owner.
Disclaimer of Liability
We have reviewed the contents of this publication to ensure consistency with the hardware and software
described. Since variance cannot be precluded entirely, we cannot guarantee full consistency. However, the
information in this publication is reviewed regularly and any necessary corrections are included in subsequent
editions.
Siemens AG
Automation and Drives
Postfach 48 48
90327 NÜRNBERG
GERMANY
A5E01469795B
Ⓟ 09/2007
Copyright © Siemens AG 2007.
Technical data subject to change

Getting Started - Advanced
Training Documents, 09/2007, A5E01469795B 3
Preface
Dear SIMATIC S7-200 user,
We created the S7-200 Getting Started manuals so that first time users can quickly and
easily learn to use the SIMATIC S7-200. Building on the Getting Started - Beginners manual
the Getting Started - Advanced manual will in a short time familiarize you with the SIMATIC
S7-200 Micro PLC. Using a few example tasks, you will learn how the controller operates
and how to create control programs for basic automatic tasks.
After working through this manual, you will find it easy to solve typical controller tasks on
your own. You can find and load the SIMATIC S7-200 program examples from the STEP 7-
Micro/WIN Documentation CD or the Programming Examples CD provided in the back cover
of this manual.
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Getting Started - Advanced
Training Documents, 09/2007, A5E01469795B 5
Table of contents
Preface................................................................................................................................................... 3
1 Quick review........................................................................................................................................... 7
1.1 A Few Words of Review ............................................................................................................. 7
1.2 Here are the Bits......................................................................................................................... 8
1.3 Power flow in a ladder diagram................................................................................................... 9
1.4 Finding information about ladder instructions ........................................................................... 10
1.5 The PLC scan cycle: Reading the inputs .................................................................................. 11
1.6 The PLC scan cycle: Writing the outputs .................................................................................. 12
1.7 The PLC scan cycle: Program logic..........................................................................................13
2 Latching................................................................................................................................................ 15
2.1 Introduction............................................................................................................................... 15
2.2 Normally Closed (NC) Contact.................................................................................................. 16
2.3 Inserting a normally-closed contact .......................................................................................... 17
2.4 Testing your circuit.................................................................................................................... 18
2.5 A faster way to create logic state latches.................................................................................. 19
2.6 Making a Set/Reset network..................................................................................................... 20
2.7 Safety Tip: How to control a machine shutdown when a wire breaks........................................ 21
3 Pulse Operated Switch.......................................................................................................................... 23
3.1 Introduction............................................................................................................................... 23
3.2 Solution Overview..................................................................................................................... 24
3.3 Edge detection.......................................................................................................................... 25
3.4 Examples of edge detection ..................................................................................................... 26
3.5 Bit memory (M addresses)........................................................................................................ 27
3.6 Pulse-operated switch .............................................................................................................. 28
3.7 Solution Description and Test................................................................................................... 29
3.8 Time to Show What You Know .................................................................................................30
4 Off Delay Timer..................................................................................................................................... 31
4.1 Introduction............................................................................................................................... 31
4.2 Save As... ................................................................................................................................. 33
4.3 Solution Overview..................................................................................................................... 34
4.4 Solution - Enter the Program .................................................................................................... 35
4.5 Solution Description.................................................................................................................. 36
4.6 Entering comments................................................................................................................... 38
4.7 Time to Show What You Know .................................................................................................41

Table of contents
Getting Started - Advanced
6 Training Documents, 09/2007, A5E01469795B
5 Sequencer ............................................................................................................................................ 43
5.1 Introduction............................................................................................................................... 43
5.2 Solution Starting Point .............................................................................................................. 44
5.3 Sequencer control..................................................................................................................... 45
5.4 Transition condition................................................................................................................... 46
5.5 Structure of the sequencer program .........................................................................................47
5.6 Control logic for the sequencer................................................................................................. 48
5.7 Working with memory bits......................................................................................................... 49
5.8 Transition condition for the sequencer...................................................................................... 50
5.9 Advantages of working with sequencers................................................................................... 51
5.10 Important safety considerations ................................................................................................ 52
5.11 Making safe transitions............................................................................................................. 53
5.12 Modification .............................................................................................................................. 54
5.13 Solution description: Transitions............................................................................................... 55
5.14 Solution description: Activating the steps.................................................................................. 56
5.15 Solution description: Activating a timer ..................................................................................... 57
5.16 Solution description: Activating the outputs ..............................................................................58
5.17 Test .......................................................................................................................................... 59
6 Learning More ...................................................................................................................................... 61
6.1 Do you Want to Learn More?.................................................................................................... 61
A Appendix A ........................................................................................................................................... 63
A.1 Bridge Circuit............................................................................................................................ 63
A.2 Diode Circuit............................................................................................................................. 64
A.3 Changeover Switch................................................................................................................... 65

Getting Started - Advanced
Training Documents, 09/2007, A5E01469795B 7
Quick review 1
1.1 A Few Words of Review
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Quick review
1.2 Here are the Bits
Getting Started - Advanced
8 Training Documents, 09/2007, A5E01469795B
1.2 Here are the Bits
The smallest unit to be processed is the bit! The bit can assume two states:
● "1" meaning "bit set" or state is "true"
● "0" meaning "bit not set " or state is "false"
In a method familiar to you, the two binary states "1" and "0" can be represented as electrical
circuits, that is, they can be represented by current flow (1) and no current flow (0).
A closed switch:
Current flows so bit state = "1"
"1" = "true" =
Current flows
and an open switch:
No current flows so bit state = "0".
"0" = "false" =
No current
flows
From here it requires only a short step
to the representation of logic operations
as circuits, e.g. series connection of
two contacts.
The AND operation of inputs I0.0 and
I0.1 is represented as shown on the
right.
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This is represented as follows in LAD:
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Finally, a small convention:
The following applies for positive logic:
24V = high-level = "1" and
0V = low-level = "0".
positive logic
The following applies for negative logic:
0V = low-level = "1"
24V = high-level = "0".
negative logic

Quick review
1.3 Power flow in a ladder diagram
Getting Started - Advanced
Training Documents, 09/2007, A5E01469795B 9
1.3 Power flow in a ladder diagram
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In this example, output Q0.3 would
be active or "1", if the contact at
I0.1 is closed, or bit value "1" (24 V
DC at input I0.1) AND
simultaneously, the timer bit T37 is
active, or "1".
Input I0.1 is now "1", and contact
I0.1 is closed. T37 is not active in
the figure, and it is a "0". Q0.3
remains inactive or "0"
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If timer T37 is also "1" (T37 has
elapsed), the result of the AND
operation is "1" and so output Q0.3
is also "1".
The output bit is then also "true", in
other words, it takes the value "1"
(gray background).
This corresponds to the LAD
status view that you have already
used in the Getting Started -
Beginnners for debugging your
program.

Quick review
1.4 Finding information about ladder instructions
Getting Started - Advanced
10 Training Documents, 09/2007, A5E01469795B
1.4 Finding information about ladder instructions
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Quick review
1.5 The PLC scan cycle: Reading the inputs
Getting Started - Advanced
Training Documents, 09/2007, A5E01469795B 11
1.5 The PLC scan cycle: Reading the inputs
All SIMATIC programmable controllers use a scan cycle. In this cyclical operation, the switch
states are read at the inputs and stored in the process input image (PII). This information is
interpreted by your control program.
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Quick review
1.6 The PLC scan cycle: Writing the outputs
Getting Started - Advanced
12 Training Documents, 09/2007, A5E01469795B
1.6 The PLC scan cycle: Writing the outputs
The outputs in the process-image output table (PIQ) are overwritten by the control logic in
the program. The bit states in the PIQ are transferred to the physical outputs in the final step.
The PLC scan cycle continuously repeats this process.
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Quick review
1.7 The PLC scan cycle: Program logic
Getting Started - Advanced
Training Documents, 09/2007, A5E01469795B 13
1.7 The PLC scan cycle: Program logic
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Getting Started - Advanced
Training Documents, 09/2007, A5E01469795B 15
Latching 2
2.1 Introduction
You should now be familiar with the standard latching function and here you will learn how to
program it.
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For example:
Output Q0.0 is to be activated
as soon as S1 at input I0.0 is
operated. With latching, Q0.0
is to remain active until S2 at
input I0.1 is operated and thus
interrupts the latch.
In STEP 7-Micro/WIN, open the first practice project "2h_pr_01.mwp" from the Programming
Exercises CD. There are still a few elements missing in the program. Add the missing LAD
elements now as a short exercise.
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To allow the latching function to work,
the output (Q0.0 in this case), must itself
ensure, as soon as it is activated, that it
retains its "true" state and therefore
remains active.
This is achieved by switching the output
(Q0.0 in this case) as a contact in
parallel to the tripping input in the same
way as a conventional contactor circuit
(Q0.0 can be compared to our contactor
K1).
Output Q0.0 as an input ensures
latching.
First add a contact Q0.0 at the point indicated as a parallel circuit to I0.0. To enter the
contact:
1. Click on the ladder diagram, (in the blank space just below the I0.0 contact and just
above "Network 2"). Then, click on the toolbar button for a contact (F4). Now click on the
normally open contact in the drop list. (As indicated on the tooltip, you can also use
function key F4 instead of the mouse). Finally, click on the address field, replace ??? with
Q0.0, then press enter.
2. To enter the vertical line, place the box cursor on the I0.0 contact, and then click on the
line down toolbar button.

Latching
2.2 Normally Closed (NC) Contact
Getting Started - Advanced
16 Training Documents, 09/2007, A5E01469795B
2.2 Normally Closed (NC) Contact
To disable the latching function, input I0.1 must break the current path when operated. If a
current path is interrupted (i.e. state "0" exists) when a switch is operated, this is referred to
as an NC contact.
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An element must be inserted
which works as an NC
contact in the ladder diagram
when there is 24 V DC
("true") at input I0.1.
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Latching
2.3 Inserting a normally-closed contact
Getting Started - Advanced
Training Documents, 09/2007, A5E01469795B 17
2.3 Inserting a normally-closed contact
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Note: Press the insert key to toggle ON the
Overwrite (OVR) mode. Look at the Status bar on
the bottom-right corner of the STEP 7- Micro/Win
window to make sure the OVR mode is set.
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1. Click the mouse to mark the LAD
diagram position with the box cursor
that shows where the NC contact will
be placed.
2. Open the Bit Logic folder in the
Instruction Tree and double click the
NC contact symbol. The NC contact is
placed in the ladder diagram
3. Finally, enter the desired NC contact
bit address (I0.1, in this case). This is
done by selecting the address field with
a mouse click and then typing the
address.
4. Always terminate text field inputs by
pressing Enter.

Latching
2.4 Testing your circuit
Getting Started - Advanced
18 Training Documents, 09/2007, A5E01469795B
2.4 Testing your circuit
As in the contactor circuit, your LAD network has an output state contact (Q0.0) connected in
parallel with the tripping element (I0.0).
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If, during a scan cycle, output
Q0.0 has been activated by
operation of switch S1 at I0.0,
contact Q0.0 parallel to I0.0 is
closed in the very next cycle
(a few milliseconds later).
This brings about latching.
NC contact I0.1 can terminate
the latch when switch S2 at
I0.1 is operated.
Save your completed program to
hard disk. Then you can load it
again at any time and continue to
edit it . (We will need the program
again for our OFF Delay example.)
Then transfer the program to the
PLC to test the function.
For test purposes, switch the PLC
to the "RUN" mode.
Test your program by operating the two switches on the input simulator connected at I0.0
and I0.1. Observe the lamps on the S7-200 or the LAD output status!
1. Begin by switching ON I0.0.
2. I0.1 must be switched OFF. The LED at I0.0 must light up.
3. Q0.0 will then light up.
4. As soon as I0.1 is switched ON, Q0.0 becomes ="0".

Latching
2.5 A faster way to create logic state latches
Getting Started - Advanced
Training Documents, 09/2007, A5E01469795B 19
2.5 A faster way to create logic state latches
Instead of feeding back the output, as in the previous example, here the
functions "Set" and "Reset" are used instead. Have a look at the ladder
diagram below.
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For the "Set" operation -(S), a
switching pulse at I0.0 has the
effect that Q0.0 is activated in a
steady state.
For the "Reset" operation -(R), a
switching pulse at I0.1 has the
effect that Q0.0 is deactivated
again.
-(S) Set
-(R) Reset
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Steady-state
setting of
value with (S)
Resetting with
(R)
Last
operation in
cycle has
priority

Latching
2.6 Making a Set/Reset network
Getting Started - Advanced
20 Training Documents, 09/2007, A5E01469795B
2.6 Making a Set/Reset network
To make sure you are using the least number of keystrokes and mouse clicks to create the
LAD networks, do the following:
1. Select the menu command Tools > Options
2. Select the Program Editor tab
3. Verify the "Enable operand editing after placing instruction" checkbox is checked
(enabled).
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You have already learned how to
enter the Normally Open contacts
I0.0 and I0.1.
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1. After marking the desired LAD
field, select the Bit Logic folder
with a single mouse click from the
list for operation families.
2. Then double click "Set" (or
"Reset") from the list of Bit Logic
operations.
3. In the already selected address
field, enter the output address
you want, Q0.0 in this case.
4. Select the lower bit field and
enter the number of bits to set
starting from address Q0.0
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