Basic Elements Of A Program - Siemens Simatic S7-200 System Manual

Create the Configuration Drawings
Based on the requirements of the functional specification, create configuration drawings of the control
equipment. Include the following items:
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Overview showing the location of each S7-200 in relation to the process or machine
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Mechanical layout of the S7-200 and expansion I/O modules (including cabinets and other
equipment)
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Electrical drawings for each S7-200 and expansion I/O module (including the device model
numbers, communications addresses, and I/O addresses)
Create a List of Symbolic Names (optional)
If you choose to use symbolic names for addressing, create a list of symbolic names for the absolute
addresses. Include not only the physical I/O signals, but also the other elements to be used in your
program.

Basic Elements of a Program

A program block is composed of executable code and comments. The executable code consists of a main
program and any subroutines or interrupt routines. The code is compiled and downloaded to the S7-200;
the program comments are not. You can use the organizational elements (main program, subroutines, and
interrupt routines) to structure your control program.
The following example shows a program that includes a subroutine and an interrupt routine. This sample
program uses a timed interrupt for reading the value of an analog input every 100 ms.
Example:Basic Elements of a Program
M
A
I
N
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B
R
0
I
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0
Programming Concepts, Conventions, and Features
Network 1 //On first scan, call subroutine 0.
LD SM0.1
CALL SBR_0
Network 1 //Set the interval to 100 ms
//for the timed interrupt.
//Enable interrupt 0.
LD SM0.0
MOVB 100, SMB34
ATCH INT_0, 10
ENI
Network 1 //Sample the Analog Input 4.
LD SM0.0
MOVW AIW4,VW100
Chapter 5
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