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Overview of an S7200 Program
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Step 7Micro/
WIN programming software supports the S7200
CPUs.
This programming package provides you with a set of features
that enable you to enter/edit, debug, and print your program;
perform program file maintenance; manipulate data in blocks, as
well as communicate with your CPU and observe status of your
program.
AMBIENT/
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Nội dung Text: Overview of an S7200 Program
- Overview of an S7200 Program
Step 7Micro/WIN programming software supports the S7200 CPUs.
This programming package provides you with a set of features
that enable you to enter/edit, debug, and print your program;
perform program file maintenance; manipulate data in blocks, as
well as communicate with your CPU and observe status of your
program.
Programming Languages
You can program the S7200 CPUs with either Ladder Logic (LAD)
or Statement List (STL) programming instructions.
Ladder Programs
In LAD programs, the basic elements of logic are represented
with contacts, coils, and boxes. A set of interconnected
elements that make a complete circuit is called a network.
A hardwired input is represented by a symbol called a contact.
A normallyopen contact enables power flow when closed. A
contact can also be normally closed. In this case, power flow
occurs when the contact is opened.
A hardwired output is represented by a symbol called a coil.
When a coil has power flow, the output is turned on.
STL Programs
STL program elements are represented by a set of instructions
for performing the desired functions. Instead of using the
graphic display as shown by ladder programs, the STL program is
shown in text format.
Executing Programs
After you download the program to the CPU, it is executed from
the first instruction through the last in a repetitive cycle,
called a scan. The CPU scan consists of reading inputs,
executing the user program, handling communication requests,
performing internal tasks, and writing outputs.
Addressing Modes
When writing your program, you can use either of two modes of
addressing instruction operands: direct or indirect.
Direct Addressing
- Direct addressing specifies the memory area and the address;
for example, VW790 refers to location 790 in V memory.
Indirect Addressing
You can address indirectly the data types I, Q, M, T, C, and V.
To do this, create a pointer to the location. Use a Move Double
Word (MOVD) instruction to move the address of a location
(pointer) to the desired destination. Use only V memory
locations or accumulator registers AC1, AC2, and AC3 as the
destination address. Place an ampersand (&) at the beginning of
the pointer address.
Use an asterisk (*) before the destination address to indicate
that the address contained in this location is to be used
instead of the value.
All pointers are double word values, and you can use them to
access byte, word, and double word values. You cannot
indirectly address bit values.
In the example below, a pointer to VB200 is created, the value
is accessed, and the pointer is incremented.
Program Structure
S7200 programs consist of a main user program that may be
followed by subroutines and/or interrupt routines. The main
program is terminated by an unconditional END (MEND in STL).
Subroutines are an optional part of a program; they must follow
the end of the main program. Interrupt routines are also
optional, and must follow the main program.
You can use interrupt routines and subroutines in any order
following the main program. However, if you group all
subroutines following the main program and all interrupt
routines immediately following the subroutines, your program
structure will be easier to read and understand. Jumps and
Subroutines enable transfer of control from one point in the
program to another.
The Jump instruction transfers control to the corresponding
Label. Both the Jump and its corresponding Label must be in the
same section of a program, either both in the main program or
both in a subroutine or interrupt routine. You cannot jump
- between program sections to a corresponding Label in another
section. For example, you cannot jump from the main program to
a corresponding Label in a subroutine.
The Subroutine is executed when it is invoked by a Call
instruction. After executing the subroutine, control returns to
the main program, and the instruction following the Call is
then executed. You can nest subroutines to eight levels.
CPU Memory
The memory in the S7200 CPUs consists of three segments:
program, data, and configurable parameters. The segments are
defined according to usage.
∙ Program memory stores the user program.
∙ Data memory includes a scratchpad area for the program and
storage of data objects. Calculations, temporary storage,
and constants reside in data memory. Additionally, data
objects, such as timers, counters, highspeed counters, and
analog inputs and outputs are stored in data memory.
∙ Configurable Parameter memory stores either the default or
the modified parameters of the program setup. The
configurable parameters include items such as protection
level, password, station address, and retentive range
information.
CPU Memory Types and Ranges
Accessed by: CPU Model 212 Ranges CPU Model 214
Ranges
Bit (Byte.bit) V 0.0 1023.7 V 0.0
4095.7
I 0.0 7.7 I 0.0 7.7
Q 0.0 7.7 Q 0.0 7.7
M 0.0 15.7 M 0.0
31.7
SM 0.0 45.7 SM 0.0
85.7
T 0 63 T 0 127
C 0 63 C 0 127
- Byte VB 0 1023 VB 0 4095
IB 0 – 7 IB 0 7
QB 0 – 7 QB 0 7
MB 0 – 15 MB 0 31
SM B 0 – 45 SM B 0 85
AC 0 – 3 AC 0 3
D ata Constants D ata Constants
W or
d VW 0 1022 VW 0 4094
T 0 – 63 T 0 127
C 0 – 63 C 0 127
I
W 0 – 6 I
W 0 6
QW 0 – 6 QW 0 6
MW 0 – 14 MW 0 30
SMW 0 – 44 SMW 0 84
AC 0 – 3 AC 0 3
AIW 0 – 30 AIW 0 30
AQW 0 – 30 AQW 0 30
D ata Constants D ata Constants
D oubl W or
e d VD 0 1020 VD 0 4092
ID 0 4 ID 0 4
QD 0 4 QD 0 4
MD 0 12 MD 0 28
SM D 0 42 SM D 0 82
AC 0 3 AC 0 3
HC 0 HC 0 2
D ata Constants D ata Constants
Guidelines
The guidelines listed below provide you with a checklist of the
major items that you can accomplish with Step 7 Micro/WIN.
CAUTION:
Always verify that your program operates correctly for your
application; i.e., insure that no safety aspects have been
overlooked in theprogram.
• Set up a project.
• Enter the application program.
• Compile and debug the program.
- • Document the program.
• Pr in t the program and documentat ion .
• Download the program to the CPU.
• Test the program.
• Set Password ( i f desi red) .
• Place CPU in Run mode.
• Monitor the appl i ca t i on with Status and Chart funct i ons .
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