1. Lecture Number 5
Siemens S7

2. In this session…
In this session, you will learn about the Siemens S7 system

3. Learning outcomes At the end of this session you should be able to:
Describe more advanced features of the S7 system
Understand the addressing system of the PLC

4. Tutorial Exercise 1 Feedback

5. Specialised Instructions Comparison, Mathematical etc.
Data word 20 of Data Block 1
Contains second comparison value.
Data word 3 of Data Block 1
Contains first comparison value.
The Multiplication instruction example multiplies the value in word 2 of DB1 by the constant +50 and stores the result in word 10 of DB1.

6. Data Formats and Data Blocks
Identifiers
2# = Binary Number
16# = Hexadecimal Number
L# = Long Decimal Number (IEEE Floating Point)
S5T# = Timer Value
C# = Counter/BCD Value
B# = Byte (8 Bit Value)
W# = Word (16 Bit Value)
DW# = Double Word (32 Bit Value)
Examples
Byte Hex B#16#FF
Word Binary 2#
Word Hex W#16#FFFF
Double Word Hex DW#16#FFFF_FFFF
Double Word Binary 2#
Integer (16 Bit) to 32767
Long Integer Word (32 Bit) L# ~ L#
IEEE Floating Point +/ e+38 ~ +/ e-38
Timer Value S5T#0H_1M_0S_0MS
Counter Value C#5
ASCII Character ‘A’

7. Data Block Example Data Block 10 (DB10) DB10.DBW8 =162 Byte Number
Data Name
Data Type
Data

8. Data Usage Example Control of Motor Via 4-20mA Analogue Output
Multiply [DB2.DBW0] by 276 and send to PQW 752.
This scales the 0%~100% to 0~27600.
This is within 0.2% of the maximum value of
Ranges will be:
0% ~ 100% From HMI User
0 ~ Generated by user programme
4 ~ 20mA Produced by Analogue Output
A scaling instruction could also be used.
Data
0-100 to DB2.DBW0
Current
4-20mA PQW752
Frequency
0Hz-50Hz
HMI sends percentage (0%-100%)
Value to Word 0 of Data Block 2.
PLC takes figure from HMI and scales it into the analogue range (0~27648) for the mA output. Value is sent to PQW 752 (analogue output).
Inverter converts mA signal into 0%-100% speed.
Motor speed is proportional to inverter output frequency.

9. Test Your Knowledge Three S7 controllers of the S7 family are?:
S7 200, S7 300, S7 400
The three main formats of the S7 software are?:
Ladder, Function Block, Statement List
The address format of S7 is?:
Byte/Bit Addressing
The data format for a 32 bit numerical value in hexadecimal is?:
DW#16#
A Data Word, Word 6 in Data Block 3, would be referenced in S7 as?:
DB3.DBW6